Templates

Revel uses Go Templates. It searches two directories for templates: * The application’s views directory (and all subdirectories) * Revel’s own templates directory.

Given a controller named Hello with an action named World, Revel will look for a template file named views/Hello/World.html. Template file names are case insensitive so views/hello/world.html will work the same as views/HeLlO/wOrLd.HtMl.

Revel provides templates for error pages (that display the friendly compilation errors in DEV mode), but the application may override them by creating a template of the equivalent name, e.g. app/views/errors/500.html.

Render Context

Revel executes the template using the RenderArgs data map. Aside from application-provided data, Revel provides the following entries:

“errors” - the map returned by Validation.ErrorMap
“flash” - the data flashed by the previous request.

Template Functions

Go provides a few functions for use in your templates. Revel adds to those. Read the documentation below or check out their source code.

eq

A simple “a == b” test.

Example:

<div class="message {{if eq .User "you"}}you{{end}}">

set

Set a variable in the given context.

Example:

{{set . "title" "Basic Chat room"}}

<h1>{{.title}}</h1>

append

Add a variable to an array, or start an array, in the given context.

Example:

{{append . "moreScripts" "js/jquery-ui-1.7.2.custom.min.js"}}

{{range .moreStyles}}
  <link rel="stylesheet" type="text/css" href="/public/{{.}}">
{{end}}

field

A helper for input fields.

Given a field name, it returns a struct containing the following members: * Id: the field name, converted to be suitable as a HTML element ID. * Name: the field name * Value: the value of the field in the current RenderArgs * Flash: the flashed value of the field. * Error: the error message, if any is associated with this field. * ErrorClass: the raw string “hasError”, if there was an error, else “”.

See godoc.

Example:

{{with $field := field "booking.CheckInDate" .}}
  <p class="{{$field.ErrorClass}}">
    <strong>Check In Date:</strong>
    <input type="text" size="10" name="{{$field.Name}}" class="datepicker" value="{{$field.Flash}}">
    * <span class="error">{{$field.Error}}</span>
  </p>
{{end}}

option

Assists in constructing HTML option elements, in conjunction with the field helper.

Example:

{{with $field := field "booking.Beds" .}}
<select name="{{$field.Name}}">
  {{option $field "1" "One king-size bed"}}
  {{option $field "2" "Two double beds"}}
  {{option $field "3" "Three beds"}}
</select>
{{end}}

radio

Assists in constructing HTML radio input elements, in conjunction with the field helper.

Example:

{{with $field := field "booking.Smoking" .}}
  {{radio $field "true"}} Smoking
  {{radio $field "false"}} Non smoking
{{end}}

nl2br

Convert newlines to HTML breaks.

Example:

You said:
<div class="comment">{{nl2br .commentText}}</div>

pluralize

A helper for correctly pluralizing words.

Example:

There are {{.numComments}} comment{{pluralize (len comments) "" "s"}}

raw

Prints raw, unescaped, text.

Example:

<div class="body">{{raw .blogBody}}</div>

Including

Go Templates allow you to compose templates by inclusion. For example:

{{template "header.html" .}}

There are two things to note: * Paths are relative to app/views

Tips

The sample applications included with Revel try to demonstrate effective use of Go Templates. In particular, please take a look at: * revel/samples/booking/app/views/header.html * revel/samples/booking/app/views/Hotels/Book.html

It takes advantage of the helper functions to set the title and extra styles in the template itself.

For example, the header looks like this:

<html>
  <head>
    <title>{{.title}}</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <link rel="stylesheet" type="text/css" media="screen" href="/public/css/main.css">
    <link rel="shortcut icon" type="image/png" href="/public/img/favicon.png">
    {{range .moreStyles}}
      <link rel="stylesheet" type="text/css" href="/public/{{.}}">
    {{end}}
    <script src="/public/js/jquery-1.3.2.min.js" type="text/javascript" charset="utf-8"></script>
    <script src="/public/js/sessvars.js" type="text/javascript" charset="utf-8"></script>
    {{range .moreScripts}}
      <script src="/public/{{.}}" type="text/javascript" charset="utf-8"></script>
    {{end}}
  </head>

And templates that include it look like this:

{{set . title "Hotels"}}
{{append . "moreStyles" "ui-lightness/jquery-ui-1.7.2.custom.css"}}
{{append . "moreScripts" "js/jquery-ui-1.7.2.custom.min.js"}}
{{template "header.html" .}}

Custom Functions

Applications may register custom functions to use in templates.

Here is an example:

func init() {
	revel.TemplateFuncs["eq"] = func(a, b interface{}) bool { return a == b }
}