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Plush

Standard Test Go Reference

Plush is the templating system that Go both needs and deserves. Powerful, flexible, and extendable, Plush is there to make writing your templates that much easier.

Introduction Video

Installation

$ go get -u github.com/gobuffalo/plush

Usage

Plush allows for the embedding of dynamic code inside of your templates. Take the following example:

<!-- input -->
<p><%= "plush is great" %></p>

<!-- output -->
<p>plush is great</p>

Controlling Output

By using the <%= %> tags we tell Plush to dynamically render the inner content, in this case the string plush is great, into the template between the <p></p> tags.

If we were to change the example to use <% %> tags instead the inner content will be evaluated and executed, but not injected into the template:

<!-- input -->
<p><% "plush is great" %></p>

<!-- output -->
<p></p>

By using the <% %> tags we can create variables (and functions!) inside of templates to use later:

<!-- does not print output -->
<%
let h = {name: "mark"}
let greet = fn(n) {
  return "hi " + n
}
%>
<!-- prints output -->
<h1><%= greet(h["name"]) %></h1>

Full Example:

html := `<html>
<%= if (names && len(names) > 0) { %>
	<ul>
		<%= for (n) in names { %>
			<li><%= capitalize(n) %></li>
		<% } %>
	</ul>
<% } else { %>
	<h1>Sorry, no names. :(</h1>
<% } %>
</html>`

ctx := plush.NewContext()
ctx.Set("names", []string{"john", "paul", "george", "ringo"})

s, err := plush.Render(html, ctx)
if err != nil {
  log.Fatal(err)
}

fmt.Print(s)
// output: <html>
// <ul>
// 		<li>John</li>
// 		<li>Paul</li>
// 		<li>George</li>
// 		<li>Ringo</li>
// 		</ul>
// </html>

Comments

You can add comments like this:

<%# This is a comment %>

You can also add line comments within a code section

<%
# this is a comment
not_a_comment()
%>

If/Else Statements

The basic syntax of if/else if/else statements is as follows:

<%
if (true) {
  # do something
} else if (false) {
  # do something
} else {
  # do something else
}
%>

When using if/else statements to control output, remember to use the <%= %> tag to output the result of the statement:

<%= if (true) { %>
  <!-- some html here -->
<% } else { %>
  <!-- some other html here -->
<% } %>

Operators

Complex if statements can be built in Plush using "common" operators:

Grouped Expressions

<%= if ((1 < 2) && (someFunc() == "hi")) { %>
  <!-- some html here -->
<% } else { %>
  <!-- some other html here -->
<% } %>

Maps

Maps in Plush will get translated to the Go type map[string]interface{} when used. Creating, and using maps in Plush is not too different than in JSON:

<% let h = {key: "value", "a number": 1, bool: true} %>

Would become the following in Go:

map[string]interface{}{
  "key": "value",
  "a number": 1,
  "bool": true,
}

Accessing maps is just like access a JSON object:

<%= h["key"] %>

Using maps as options to functions in Plush is incredibly powerful. See the sections on Functions and Helpers to see more examples.

Arrays

Arrays in Plush will get translated to the Go type []interface{} when used.

<% let a = [1, 2, "three", "four", h] %>

[]interface{}{ 1, 2, "three", "four", h }

For Loops

There are three different types that can be looped over: maps, arrays/slices, and iterators. The format for them all looks the same:

<%= for (key, value) in expression { %>
  <%= key %> <%= value %>
<% } %>

You can also continue to the next iteration of the loop:

for (i,v) in [1, 2, 3,4,5,6,7,8,9,10] {
  if (i > 0) {
    continue
  }
  return v
}

You can terminate the for loop with break:

for (i,v) in [1, 2, 3,4,5,6,7,8,9,10] {
  if (i > 5) {
    break
  }
  return v
}

The values inside the () part of the statement are the names you wish to give to the key (or index) and the value of the expression. The expression can be an array, map, or iterator type.

Arrays

Using Index and Value

<%= for (i, x) in someArray { %>
  <%= i %> <%= x %>
<% } %>

Using Just the Value

<%= for (val) in someArray { %>
  <%= val %>
<% } %>

Maps

Using Index and Value

<%= for (k, v) in someMap { %>
  <%= k %> <%= v %>
<% } %>

Using Just the Value

<%= for (v) in someMap { %>
  <%= v %>
<% } %>

Iterators

type ranger struct {
	pos int
	end int
}

func (r *ranger) Next() interface{} {
	if r.pos < r.end {
		r.pos++
		return r.pos
	}
	return nil
}

func betweenHelper(a, b int) Iterator {
	return &ranger{pos: a, end: b - 1}
}

html := `<%= for (v) in between(3,6) { return v } %>`

ctx := plush.NewContext()
ctx.Set("between", betweenHelper)

s, err := plush.Render(html, ctx)
if err != nil {
  log.Fatal(err)
}
fmt.Print(s)
// output: 45

Default helpers

Plush ships with a comprehensive list of helpers to make your life easier. For more info check the helpers package.

Custom Helpers

html := `<p><%= one() %></p>
<p><%= greet("mark")%></p>
<%= can("update") { %>
<p>i can update</p>
<% } %>
<%= can("destroy") { %>
<p>i can destroy</p>
<% } %>
`

ctx := NewContext()

// one() #=> 1
ctx.Set("one", func() int {
  return 1
})

// greet("mark") #=> "Hi mark"
ctx.Set("greet", func(s string) string {
  return fmt.Sprintf("Hi %s", s)
})

// can("update") #=> returns the block associated with it
// can("adsf") #=> ""
ctx.Set("can", func(s string, help HelperContext) (template.HTML, error) {
  if s == "update" {
    h, err := help.Block()
    return template.HTML(h), err
  }
  return "", nil
})

s, err := Render(html, ctx)
if err != nil {
  log.Fatal(err)
}
fmt.Print(s)
// output: <p>1</p>
// <p>Hi mark</p>
// <p>i can update</p>

Special Thanks

This package absolutely 100% could not have been written without the help of Thorsten Ball's incredible book, Writing an Interpeter in Go.

Not only did the book make understanding the process of writing lexers, parsers, and asts, but it also provided the basis for the syntax of Plush itself.

If you have yet to read Thorsten's book, I can't recommend it enough. Please go and buy it!