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 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, *args, **kwargs, &block) ⇒ Object

Delegates all unhandled calls to object returned by #document method.

Parameters:

  • method_name (Symbol)
  • args (Array) —

    Positional arguments.

  • kwargs (Hash) —

    Keyword arguments.

  • block (Proc)
Source Code
lib/prawn/view.rb, line 75
75
def method_missing(method_name, *args, **kwargs, &block)

76
  return super unless document.respond_to?(method_name)

77
78
  document.public_send(method_name, *args, **kwargs, &block)

79
end







  




  

    
Instance Method Details


    
      

  

  
    #document  ⇒ Prawn::Dcoument 
  

  

  


  

    
Lazily instantiates a Prawn::Document object.



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



  





  


Returns:


    
  
    
  • 
      
      
        (Prawn::Dcoument)
      
      
      
    
    • 
  







  Source Code
  
lib/prawn/view.rb, line 65

  
65
def document

66
  @document ||= Prawn::Document.new

67
end







    
      

  

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

  

  


  

    
Does this object respond to the specified message?



  





  

Parameters:


    
  
    
  • 
      
        method_name
      
      
        (Symbol)
      
      
      
    
    • 
  
    
  • 
      
        _include_all
      
      
        (Boolean)
      
      
        (defaults to: false)
      
      
    
    • 
  




Returns:


    
  
    
  • 
      
      
        (Boolean)
      
      
      
    
    • 
  







  Source Code
  
lib/prawn/view.rb, line 86

  
86
def respond_to_missing?(method_name, _include_all = false)

87
  document.respond_to?(method_name) || super

88
end







    
      

  

  
    #save_as(filename)  ⇒ void 
  

  

  


  

    
This method returns an undefined value.
Syntatic sugar that calls document.render_file under the hood.



  





  
  

    
Examples:

    
      
      
greeter.save_as("greetings.pdf")


    
  



Parameters:


    
  
    
  • 
      
        filename
      
      
        (String)
      
      
      
    
    • 
  








  Source Code
  
lib/prawn/view.rb, line 112

  
112
def save_as(filename)

113
  document.render_file(filename)

114
end







    
      

  

  
    #update { ... } ⇒ void 
  

  

  


  

    
This method returns an undefined value.
Syntactic sugar that uses instance_eval under the hood to provide
a block-based DSL.



  





  
  

    
Examples:

    
      
      
greeter.update do
  say_hello
  say_goodbye
end


    
  




Yields:


    
  
    
  • 
      
      
        
      
      
      
    
    • 
  







  Source Code
  
lib/prawn/view.rb, line 101

  
101
def update(&block)

102
  instance_eval(&block)

103
end