delegates
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delegate :methods, to: :target, extracted from ActiveSupport
Delegates
This gem is just an extraction of the handy delegate :method1, :method2, method3, to: :receiver from ActiveSupport. It seems to be seriously superior to stdlib's Forwardable, and sometimes I want it in contexts when ActiveSupport and monkey-patching is undesireable.
Usage:
gem install delegates
(or add gem 'delegates' to your Gemfile).
Then:
class Employee < Struct.new(:name, :department, :address)
# ...
extend Delegates
delegate :city, :street, to: :address
# ...
end
employee = Employee.new(name, department, address)
employee.city # will call employee.address.city
to: can be anything evaluatable from inside the class: :<CONSTANT>, :@<instance_variable>, 'chain.of.calls' etc.; special names requiring self (like class method) handled gracefully with just delegate ..., to: :class. New methods are defined with eval-ing strings, so they are as fast as if manually written.
Supported options examples (all that ActiveSupport's Module#delegate supports):
delegate :city, to: :address, prefix: true # defined method would be address_city
delegate :city, to: :address, prefix: :adrs # defined method would be adrs_city
delegate :city, to: :address, private: true # defined method would be private
delegate :city, to: :address, allow_nil: true
The latter option will handle the employee.city call when employee.address is nil by returning nil; otherwise (by default) informative DelegationError is raised.
Credits
99.99% of credits should go to Rails users and contributors, who found and and handled miriads of realistic edge cases. I just copied the code (and groomed it a bit for closer to my own style).