Module: Prawn::View

Defined in:
lib/prawn/view.rb

Overview

This mixin allows you to create modular Prawn code without the need to create subclasses of Prawn::Document.

 class Greeter
   include Prawn::View

   # Optional override: allows you to set document options or even use
   # a custom document class
   def document
     @document ||= Prawn::Document.new(page_size: 'A4')
   end

   def initialize(name)
     @name = name
   end

   def say_hello
     text "Hello, #{@name}!"
   end

   def say_goodbye
     font("Courier") do
       text "Goodbye, #{@name}!"
     end
   end
end

greeter = Greeter.new("Gregory")

greeter.say_hello
greeter.say_goodbye

greeter.save_as("greetings.pdf")

The short story about why you should use this mixin rather than creating subclasses of Prawn::Document is that it helps prevent accidental conflicts between your code and Prawn’s code.

Here’s the slightly longer story…

By using composition rather than inheritance under the hood, this mixin allows you to keep your state separate from Prawn::Document‘s state, and also will prevent unexpected method name collisions due to late binding effects.

This mixin is mostly meant for extending Prawn’s functionality with your own additions, but you can also use it to replace or wrap existing Prawn methods. Calling super will still work as expected, and alternatively you can explicitly call document.some_method to delegate to Prawn where needed.

Experimental API collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method_name, *arguments, &block) ⇒ Object

Delegates all unhandled calls to object returned by document method. (which is an instance of Prawn::Document by default)



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# File 'lib/prawn/view.rb', line 72

def method_missing(method_name, *arguments, &block)
  return super unless document.respond_to?(method_name)

  document.public_send(method_name, *arguments, &block)
end

Instance Method Details

#document ⇒ Object

Lazily instantiates a Prawn::Document object.

You can also redefine this method in your own classes to use a custom document class.



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# File 'lib/prawn/view.rb', line 66

def document
  @document ||= Prawn::Document.new
end

#respond_to_missing?(method_name, _include_all = false) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/prawn/view.rb', line 78

def respond_to_missing?(method_name, _include_all = false)
  document.respond_to?(method_name) || super
end

#save_as(filename) ⇒ Object

Syntatic sugar that calls document.render_file under the hood.

greeter.save_as("greetings.pdf")



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# File 'lib/prawn/view.rb', line 97

def save_as(filename)
  document.render_file(filename)
end

#update(&block) ⇒ Object

Syntactic sugar that uses instance_eval under the hood to provide a block-based DSL.

greeter.update do
  say_hello
  say_goodbye
end



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# File 'lib/prawn/view.rb', line 90

def update(&block)
  instance_eval(&block)
end