Rendering Templates

To render a template, simply call the #render method on the template:

Hello = -> { h1 "Hello" }
Hello.render
#=> "<h1>Hello</h1>"

Passing Parameters

When a template takes one or more arguments, you should pass the corresponding parameters to #render:

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

As with any normal Ruby method call, you can pass rest parameters and keyword parameters to #render, and they will be passed to the template:

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

def render_hello(*args)
  Hello.render(*args)
end

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

Passing a Block

The #render method 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 }
}

DivWrapper.render { 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 parameters to an existing template using the #apply method:

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

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