Rendering Templates

To render a template, use Papercraft.html and pass in the template:

Hello = -> { h1 "Hello" }
Papercraft.html(Hello)
#=> "<h1>Hello</h1>"

Alternatively you can also render HTML inline by passing a template as a block:

Papercraft.html {
  h1 "Hello"
}
#=> "<h1>Hello</h1>"

Passing Arguments

When a template takes one or more arguments, they should be passed to Papercraft.html following the template reference:

Hello = ->(name) { h1 "Hello, #{name}!" }
Papercraft.html(Hello, "world") #=> "<h1>Hello, world!</h1>"

As with any normal Ruby method call, you can pass rest arguments and keyword arguments to Papercraft.html, and they will be passed to the template:

Hello = ->(name) { h1 "Hello, #{name}!" }

def render_hello(*args)
  Papercraft.html(Hello, *args)
end

render_hello("world") #=> "<h1>Hello, world!</h1>"

Passing a Block

Papercraft.html can also be given a block, which will be passed to the template. Such a block can be used for rendering inner elements inside the template. To render the passed block, the template should call render_children or render_yield:

DivWrapper = -> {
  div { render_yield }
}

Papercraft.html(DivWrapper) { h1 "Hello!" }
#=> "<div><h1>Hello!</h1></div>"

The difference between render_yield and render_children is that render_yield will raise an exception if no block is given when rendering.

Creating Derived Templates with Parameter Application

One of the advantages of expressing templates as lambdas is that you can create derivative templates very easily by applying arguments to an existing template using the #apply method:

# original template:
Hello = ->(name) { h1 "Hello, #{name}!" }
Papercraft.html(Hello, "world")
#=> "<h1>Hello, world!</h1>"

# derived template:
HelloWorld = Papercraft.apply(Hello, "world")
Papercraft.html(HelloWorld)
#=> "<h1>Hello, world!</h1>"

Rendering XML templates

Papercraft also has experimental support for rendering XML templates, for example RSS feeds. To render a template as XML, use Papercraft.xml:

rss_feed = ->() {
  rss(version: '2.0', 'xmlns:atom' => 'http://www.w3.org/2005/Atom') {
    channel {
      title 'My blog'
      link 'https://myblog.com/'
      description 'My blog'
      language 'en-us'
      pubDate Time.now.httpdate
      ...
    }
  }
}
Papercraft.xml(rss_feed)

Cached rendering of templates

Papercraft also provides a mechanism for caching rendered templates, using Papercraft.cache_html. This method takes an additional parameter used as cache key. It is the responsibility of the caller to provide a cache key:

Papercraft.cache_html(template, cache_key, ...)