DslAccessor

This plugin gives hybrid accessor class methods to classes by DSL like definition, here hybrid means getter and setter. The accessor method acts as getter method if no argments given, otherwise it acts as setter one with the arguments.

Usage

class Foo
  dsl_accessor "<METHOD NAME>"
end

Example

class Foo
  dsl_accessor :greeting
end

This code gives ‘greeting’ class method to Foo class.

Foo.greeting                 # means getter, and the default value is nil.
=> nil

Foo.greeting "I'm Foo."      # means setter with given arguments
=> "I'm Foo."

Foo.greeting
=> "I'm Foo."

Difference

I’m convinced that you want to propose me to use ‘cattr_accessor’. Although the difference is just whether we needs ‘=’ operation or not, it makes a large different on class definition especially subclass.

class Foo
  cattr_accessor :greeting
end

class Bar < Foo
  self.greeting = "I'm bar."
end

We must write redundant code represented by “self.” to distinguish a local variable and a class method when we use ‘cattr_accessor’. This is ugly and boring work.

class Foo
  dsl_accessor :greeting
end

class Bar < Foo
  greeting "I'm bar."
end

There are no longer redundant prefix code like “self.” and “set_”. Don’t you like this dsl-like coding with simple declaration?

Special Options

‘dsl_accessor’ method can take two options, those are :writer and :default. “writer” option means callback method used when setter is executed. “default” option means default static value or proc that creates some value.

class PseudoAR
  dsl_accessor :primary_key, :default=>"id", :writer=>proc{|value| value.to_s}
  dsl_accessor :table_name,  :default=>proc{|klass| klass.name.demodulize.underscore.pluralize}
end

class Item < PseudoAR
end

class User < PseudoAR
  primary_key :user_code
  table_name  :user_table
end

Item.primary_key  # => "id"
Item.table_name   # => "items"
User.primary_key  # => "user_code"
User.table_name   # => :user_table

Note that “User.primary_key” return a String by setter proc.

Instance Method

“instance” option automatically defines its instance method

class Search
  dsl_accessor :url, :instance=>true, :default=>"http://localhost/"
end

Search.url       # => "http://localhost/"
Search.new.url   # => "http://localhost/"

and it uses @options instance variable with special value :options

class Window
  dsl_accessor :width, :default=>640, :instance=>:options
  def initialize(options = {})
    @options = options
  end
end

Window.width       # => 640
Window.new.width   # => 640

window = Window.new(:width=>320)
window.width       # =>320

Install

git://github.com/maiha/dsl_accessor.git

Auto declared mode

Calling dsl_accessor without args enters auto declared mode. In this mode, a method missing means instance method creation. This affects only methods with a block and no other args.

class Foo
  dsl_accessor		# auto declared mode
    foo{1}      		# define :foo
    bar(a)			# NoMethodError
    baz(a){2}			# NoMethodError
end

Foo.new.foo # => 1

This is useful when you have many methods those are one lined methods.

[without auto delared mode]
class Foo
  def last
    num_pages
  end

  def first?
    page == 1
  end

  def offset
    model.proxy_options[:offset]
  end
end

[with auto delared mode]
class Foo
  dsl_accessor
    last   {num_pages}
    first? {page == 1}
    offset {model.proxy_options[:offset]}
end

Author

Maiha <maiha@wota.jp>