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.

“‘ruby 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) 


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# File 'lib/prawn/view.rb', line 75

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

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


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# File 'lib/prawn/view.rb', line 65

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


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# File 'lib/prawn/view.rb', line 86

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


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# File 'lib/prawn/view.rb', line 112

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



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# File 'lib/prawn/view.rb', line 101

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