module Prawn::View
This mixin allows you to create modular Prawn
code without the need to create subclasses of Prawn::Document
.
class Greeter include Prawn::View 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 explictly call document.some_method
to delegate to Prawn
where needed.
Public Instance Methods
Lazily instantiates a Prawn::Document
object.
You can also redefine this method in your own classes to use a custom document class.
# File lib/prawn/view.rb, line 58 def document @document ||= Prawn::Document.new end
Delegates all unhandled calls to object returned by document
method. (which is an instance of Prawn::Document
by default)
# File lib/prawn/view.rb, line 64 def method_missing(m, *a, &b) return super unless document.respond_to?(m) document.send(m, *a, &b) end
# File lib/prawn/view.rb, line 70 def respond_to_missing? document.respond_to?(m) end
Syntatic sugar that calls document.render_file
under the hood.
greeter.save_as("greetings.pdf")
# File lib/prawn/view.rb, line 89 def save_as(filename) document.render_file(filename) end
Syntactic sugar that uses instance_eval
under the hood to provide a block-based DSL.
greeter.update do say_hello say_goodbye end
# File lib/prawn/view.rb, line 82 def update(&b) instance_eval(&b) end