open-consul/ui/packages/consul-ui/app/helpers/render-template.mdx
John Cowen 764c22a6c4
ui: Add eng docs for our render-template helper (#11359)
Adds Engineer documentation for our recently improved render-template helper, plus some ideas for further work/improvement here should anyone ever want to pick that up.
2021-11-18 10:21:36 +00:00

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# render-template
`{{render-template 'template string' vars}}` is used to interpolate some dynamic
variables into a string and produce a string output as a result i.e. a micro,
regex based, template engine. For example:
```hbs preview-template
<figure>
{{render-template 'http://localhost/?service={{Service.Name}}&datacenter={{Datacenter}}'
(hash
Datacenter="dc1"
Service=(hash
Name="Hello-Service"
)
)
}}
<figcaption>^ that is the rendered template</figcaption>
</figure>
```
Additionally the variables passed into the template are automatically URL
encoded as our primary usecase for this is for creating dynamic links/URLs. If
we ever need to reuse this without URL encoding, then an option could be added
as a named argument to disable/turn that off. In which case, encode should be
default and a knob provided to turn it off (at the time of writing our primary
usecase is to encode).
Currently supported separators are mustache style `{{VariableName}}`, although
we would like to add Javascript style `${VariableName}` separators in the future
and transition to default to those whilst remaining backwards compatible.
Mustache style are a documentated user 'feature' for some Consul config, so we
should be mindful of that.
**Please note:** Our `uri` helper (that is used extensively in the UI) also uses
some of the underlying functionality of `render-template` via our `encoder`
service.
## Positional Arguments
| Argument | Type | Default | Description |
| --- | --- | --- | --- |
| `template` | `String` | | A template string for the variables to be interpolated into |
| `vars` | `Object` | | An object/hash of variables to URL encode and interpolate into the template string |