577 lines
15 KiB
Go
577 lines
15 KiB
Go
// Package structs contains various utilities functions to work with structs.
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package structs
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import (
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"fmt"
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"reflect"
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)
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var (
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// DefaultTagName is the default tag name for struct fields which provides
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// a more granular to tweak certain structs. Lookup the necessary functions
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// for more info.
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DefaultTagName = "structs" // struct's field default tag name
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)
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// Struct encapsulates a struct type to provide several high level functions
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// around the struct.
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type Struct struct {
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raw interface{}
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value reflect.Value
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TagName string
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}
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// New returns a new *Struct with the struct s. It panics if the s's kind is
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// not struct.
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func New(s interface{}) *Struct {
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return &Struct{
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raw: s,
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value: strctVal(s),
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TagName: DefaultTagName,
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}
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}
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// Map converts the given struct to a map[string]interface{}, where the keys
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// of the map are the field names and the values of the map the associated
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// values of the fields. The default key string is the struct field name but
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// can be changed in the struct field's tag value. The "structs" key in the
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// struct's field tag value is the key name. Example:
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//
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// // Field appears in map as key "myName".
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// Name string `structs:"myName"`
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//
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// A tag value with the content of "-" ignores that particular field. Example:
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//
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// // Field is ignored by this package.
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// Field bool `structs:"-"`
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//
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// A tag value with the content of "string" uses the stringer to get the value. Example:
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//
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// // The value will be output of Animal's String() func.
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// // Map will panic if Animal does not implement String().
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// Field *Animal `structs:"field,string"`
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//
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// A tag value with the option of "flatten" used in a struct field is to flatten its fields
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// in the output map. Example:
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//
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// // The FieldStruct's fields will be flattened into the output map.
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// FieldStruct time.Time `structs:",flatten"`
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//
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// A tag value with the option of "omitnested" stops iterating further if the type
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// is a struct. Example:
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//
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// // Field is not processed further by this package.
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// Field time.Time `structs:"myName,omitnested"`
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// Field *http.Request `structs:",omitnested"`
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//
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// A tag value with the option of "omitempty" ignores that particular field if
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// the field value is empty. Example:
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//
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// // Field appears in map as key "myName", but the field is
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// // skipped if empty.
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// Field string `structs:"myName,omitempty"`
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//
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// // Field appears in map as key "Field" (the default), but
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// // the field is skipped if empty.
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// Field string `structs:",omitempty"`
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//
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// Note that only exported fields of a struct can be accessed, non exported
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// fields will be neglected.
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func (s *Struct) Map() map[string]interface{} {
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out := make(map[string]interface{})
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s.FillMap(out)
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return out
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}
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// FillMap is the same as Map. Instead of returning the output, it fills the
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// given map.
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func (s *Struct) FillMap(out map[string]interface{}) {
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if out == nil {
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return
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}
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fields := s.structFields()
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for _, field := range fields {
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name := field.Name
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val := s.value.FieldByName(name)
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isSubStruct := false
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var finalVal interface{}
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tagName, tagOpts := parseTag(field.Tag.Get(s.TagName))
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if tagName != "" {
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name = tagName
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}
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// if the value is a zero value and the field is marked as omitempty do
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// not include
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if tagOpts.Has("omitempty") {
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zero := reflect.Zero(val.Type()).Interface()
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current := val.Interface()
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if reflect.DeepEqual(current, zero) {
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continue
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}
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}
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if !tagOpts.Has("omitnested") {
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finalVal = s.nested(val)
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v := reflect.ValueOf(val.Interface())
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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switch v.Kind() {
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case reflect.Map, reflect.Struct:
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isSubStruct = true
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}
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} else {
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finalVal = val.Interface()
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}
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if tagOpts.Has("string") {
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s, ok := val.Interface().(fmt.Stringer)
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if ok {
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out[name] = s.String()
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}
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continue
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}
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if isSubStruct && (tagOpts.Has("flatten")) {
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for k := range finalVal.(map[string]interface{}) {
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out[k] = finalVal.(map[string]interface{})[k]
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}
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} else {
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out[name] = finalVal
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}
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}
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}
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// Values converts the given s struct's field values to a []interface{}. A
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// struct tag with the content of "-" ignores the that particular field.
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// Example:
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//
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// // Field is ignored by this package.
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// Field int `structs:"-"`
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//
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// A value with the option of "omitnested" stops iterating further if the type
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// is a struct. Example:
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//
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// // Fields is not processed further by this package.
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// Field time.Time `structs:",omitnested"`
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// Field *http.Request `structs:",omitnested"`
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//
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// A tag value with the option of "omitempty" ignores that particular field and
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// is not added to the values if the field value is empty. Example:
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//
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// // Field is skipped if empty
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// Field string `structs:",omitempty"`
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//
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// Note that only exported fields of a struct can be accessed, non exported
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// fields will be neglected.
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func (s *Struct) Values() []interface{} {
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fields := s.structFields()
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var t []interface{}
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for _, field := range fields {
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val := s.value.FieldByName(field.Name)
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_, tagOpts := parseTag(field.Tag.Get(s.TagName))
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// if the value is a zero value and the field is marked as omitempty do
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// not include
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if tagOpts.Has("omitempty") {
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zero := reflect.Zero(val.Type()).Interface()
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current := val.Interface()
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if reflect.DeepEqual(current, zero) {
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continue
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}
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}
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if tagOpts.Has("string") {
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s, ok := val.Interface().(fmt.Stringer)
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if ok {
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t = append(t, s.String())
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}
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continue
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}
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if IsStruct(val.Interface()) && !tagOpts.Has("omitnested") {
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// look out for embedded structs, and convert them to a
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// []interface{} to be added to the final values slice
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for _, embeddedVal := range Values(val.Interface()) {
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t = append(t, embeddedVal)
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}
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} else {
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t = append(t, val.Interface())
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}
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}
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return t
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}
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// Fields returns a slice of Fields. A struct tag with the content of "-"
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// ignores the checking of that particular field. Example:
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//
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// // Field is ignored by this package.
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// Field bool `structs:"-"`
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//
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// It panics if s's kind is not struct.
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func (s *Struct) Fields() []*Field {
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return getFields(s.value, s.TagName)
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}
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// Names returns a slice of field names. A struct tag with the content of "-"
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// ignores the checking of that particular field. Example:
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//
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// // Field is ignored by this package.
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// Field bool `structs:"-"`
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//
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// It panics if s's kind is not struct.
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func (s *Struct) Names() []string {
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fields := getFields(s.value, s.TagName)
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names := make([]string, len(fields))
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for i, field := range fields {
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names[i] = field.Name()
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}
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return names
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}
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func getFields(v reflect.Value, tagName string) []*Field {
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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t := v.Type()
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var fields []*Field
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for i := 0; i < t.NumField(); i++ {
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field := t.Field(i)
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if tag := field.Tag.Get(tagName); tag == "-" {
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continue
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}
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f := &Field{
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field: field,
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value: v.FieldByName(field.Name),
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}
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fields = append(fields, f)
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}
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return fields
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}
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// Field returns a new Field struct that provides several high level functions
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// around a single struct field entity. It panics if the field is not found.
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func (s *Struct) Field(name string) *Field {
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f, ok := s.FieldOk(name)
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if !ok {
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panic("field not found")
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}
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return f
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}
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// FieldOk returns a new Field struct that provides several high level functions
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// around a single struct field entity. The boolean returns true if the field
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// was found.
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func (s *Struct) FieldOk(name string) (*Field, bool) {
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t := s.value.Type()
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field, ok := t.FieldByName(name)
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if !ok {
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return nil, false
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}
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return &Field{
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field: field,
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value: s.value.FieldByName(name),
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defaultTag: s.TagName,
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}, true
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}
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// IsZero returns true if all fields in a struct is a zero value (not
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// initialized) A struct tag with the content of "-" ignores the checking of
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// that particular field. Example:
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//
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// // Field is ignored by this package.
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// Field bool `structs:"-"`
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//
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// A value with the option of "omitnested" stops iterating further if the type
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// is a struct. Example:
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//
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// // Field is not processed further by this package.
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// Field time.Time `structs:"myName,omitnested"`
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// Field *http.Request `structs:",omitnested"`
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//
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// Note that only exported fields of a struct can be accessed, non exported
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// fields will be neglected. It panics if s's kind is not struct.
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func (s *Struct) IsZero() bool {
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fields := s.structFields()
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for _, field := range fields {
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val := s.value.FieldByName(field.Name)
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_, tagOpts := parseTag(field.Tag.Get(s.TagName))
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if IsStruct(val.Interface()) && !tagOpts.Has("omitnested") {
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ok := IsZero(val.Interface())
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if !ok {
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return false
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}
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continue
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}
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// zero value of the given field, such as "" for string, 0 for int
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zero := reflect.Zero(val.Type()).Interface()
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// current value of the given field
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current := val.Interface()
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if !reflect.DeepEqual(current, zero) {
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return false
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}
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}
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return true
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}
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// HasZero returns true if a field in a struct is not initialized (zero value).
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// A struct tag with the content of "-" ignores the checking of that particular
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// field. Example:
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//
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// // Field is ignored by this package.
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// Field bool `structs:"-"`
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//
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// A value with the option of "omitnested" stops iterating further if the type
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// is a struct. Example:
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//
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// // Field is not processed further by this package.
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// Field time.Time `structs:"myName,omitnested"`
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// Field *http.Request `structs:",omitnested"`
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//
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// Note that only exported fields of a struct can be accessed, non exported
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// fields will be neglected. It panics if s's kind is not struct.
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func (s *Struct) HasZero() bool {
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fields := s.structFields()
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for _, field := range fields {
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val := s.value.FieldByName(field.Name)
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_, tagOpts := parseTag(field.Tag.Get(s.TagName))
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if IsStruct(val.Interface()) && !tagOpts.Has("omitnested") {
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ok := HasZero(val.Interface())
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if ok {
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return true
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}
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continue
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}
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// zero value of the given field, such as "" for string, 0 for int
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zero := reflect.Zero(val.Type()).Interface()
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// current value of the given field
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current := val.Interface()
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if reflect.DeepEqual(current, zero) {
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return true
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}
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}
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return false
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}
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// Name returns the structs's type name within its package. For more info refer
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// to Name() function.
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func (s *Struct) Name() string {
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return s.value.Type().Name()
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}
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// structFields returns the exported struct fields for a given s struct. This
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// is a convenient helper method to avoid duplicate code in some of the
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// functions.
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func (s *Struct) structFields() []reflect.StructField {
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t := s.value.Type()
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var f []reflect.StructField
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for i := 0; i < t.NumField(); i++ {
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field := t.Field(i)
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// we can't access the value of unexported fields
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if field.PkgPath != "" {
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continue
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}
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// don't check if it's omitted
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if tag := field.Tag.Get(s.TagName); tag == "-" {
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continue
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}
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f = append(f, field)
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}
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return f
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}
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func strctVal(s interface{}) reflect.Value {
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v := reflect.ValueOf(s)
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// if pointer get the underlying element≤
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for v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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if v.Kind() != reflect.Struct {
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panic("not struct")
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}
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return v
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}
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// Map converts the given struct to a map[string]interface{}. For more info
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// refer to Struct types Map() method. It panics if s's kind is not struct.
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func Map(s interface{}) map[string]interface{} {
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return New(s).Map()
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}
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// FillMap is the same as Map. Instead of returning the output, it fills the
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// given map.
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func FillMap(s interface{}, out map[string]interface{}) {
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New(s).FillMap(out)
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}
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// Values converts the given struct to a []interface{}. For more info refer to
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// Struct types Values() method. It panics if s's kind is not struct.
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func Values(s interface{}) []interface{} {
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return New(s).Values()
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}
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// Fields returns a slice of *Field. For more info refer to Struct types
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// Fields() method. It panics if s's kind is not struct.
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func Fields(s interface{}) []*Field {
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return New(s).Fields()
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}
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// Names returns a slice of field names. For more info refer to Struct types
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// Names() method. It panics if s's kind is not struct.
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func Names(s interface{}) []string {
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return New(s).Names()
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}
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// IsZero returns true if all fields is equal to a zero value. For more info
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// refer to Struct types IsZero() method. It panics if s's kind is not struct.
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func IsZero(s interface{}) bool {
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return New(s).IsZero()
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}
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// HasZero returns true if any field is equal to a zero value. For more info
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// refer to Struct types HasZero() method. It panics if s's kind is not struct.
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func HasZero(s interface{}) bool {
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return New(s).HasZero()
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}
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// IsStruct returns true if the given variable is a struct or a pointer to
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// struct.
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func IsStruct(s interface{}) bool {
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v := reflect.ValueOf(s)
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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// uninitialized zero value of a struct
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if v.Kind() == reflect.Invalid {
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return false
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}
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return v.Kind() == reflect.Struct
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}
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// Name returns the structs's type name within its package. It returns an
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// empty string for unnamed types. It panics if s's kind is not struct.
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func Name(s interface{}) string {
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return New(s).Name()
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}
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// nested retrieves recursively all types for the given value and returns the
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// nested value.
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func (s *Struct) nested(val reflect.Value) interface{} {
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var finalVal interface{}
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v := reflect.ValueOf(val.Interface())
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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switch v.Kind() {
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case reflect.Struct:
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n := New(val.Interface())
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n.TagName = s.TagName
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m := n.Map()
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// do not add the converted value if there are no exported fields, ie:
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// time.Time
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if len(m) == 0 {
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finalVal = val.Interface()
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} else {
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finalVal = m
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}
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case reflect.Map:
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v := val.Type().Elem()
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if v.Kind() == reflect.Ptr {
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v = v.Elem()
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}
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// only iterate over struct types, ie: map[string]StructType,
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// map[string][]StructType,
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if v.Kind() == reflect.Struct ||
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(v.Kind() == reflect.Slice && v.Elem().Kind() == reflect.Struct) {
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m := make(map[string]interface{}, val.Len())
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for _, k := range val.MapKeys() {
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m[k.String()] = s.nested(val.MapIndex(k))
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}
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finalVal = m
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break
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}
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// TODO(arslan): should this be optional?
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finalVal = val.Interface()
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case reflect.Slice, reflect.Array:
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if val.Type().Kind() == reflect.Interface {
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finalVal = val.Interface()
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break
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}
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// TODO(arslan): should this be optional?
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// do not iterate of non struct types, just pass the value. Ie: []int,
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// []string, co... We only iterate further if it's a struct.
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if val.Type().Elem().Kind() != reflect.Struct {
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finalVal = val.Interface()
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break
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}
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slices := make([]interface{}, val.Len(), val.Len())
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for x := 0; x < val.Len(); x++ {
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slices[x] = s.nested(val.Index(x))
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|
}
|
|
finalVal = slices
|
|
default:
|
|
finalVal = val.Interface()
|
|
}
|
|
|
|
return finalVal
|
|
}
|