Do you imagin how attr_accessor is implemented in Ruby? Let’s implement it by yourself.
My attr_accessor module
Create CustomAttrAccessor module which overrides Ruby’s attr_accessor method.
module CustomAttrAccessor
def self.included(base)
base.extend ClassMethods
end
module ClassMethods
def attr_accessor(attr)
define_method(attr) do
puts "trying to get @#{attr}"
instance_variable_get "@#{attr}"
end
define_method("#{attr}=") do |value|
instance_variable_set "@#{attr}", value
puts "@#{attr} has been set"
end
end
end
end
inlcude attr_accessor module
You can use your custom attr_accessor by including the module you’ve created in the class.
class A
include CustomAttrAccessor
attr_accessor :bar
end
Test your attr_accessor
Let’s test the attr_accessor.
a = A.new
val = a.bar # trying to get @bar
p val # => nil
a.bar = "my value" # @bar has been set
val = a.bar # trying to get @bar
p val # => "my value"
Ruby Technique: Class Macro
You can create your own class macro like the following:
module ClassMacro
def self.included(base)
base.extend ClassMethods
end
module ClassMethods
def my_class_macro
puts "my_class_macro!"
end
end
end
class Macro
include ClassMacro
my_class_macro # => my_class_macro!
end