This article will discuss a very useful method in Ruby on Rails - ActiveRecord, i.e. delegate. According to the documentation, delegate:
provides a delegate class method to easily expose contained objects’ public methods as your own.
Here’s an example: Assume you have a user model that has one object of the address model. The address model contains address1, address2, city, state, and zip as attributes. Create these models first.
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rails g model User name
rails g model Address address1 address2 city state zip user:belongs_to
rails db:migrate
In the user.rb, put this:
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has_one :address
In address.rb, put the following method:
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def formatted_address
address1.to_s + ' ' + address2.to_s + ' ' + city.to_s + ',' + ' ' + state.to_s + ' ' + zip.to_s
end
Now create one record each for the specified models.
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rails console
User.create(name: "John")
user = User.first
user.create_address(address1: "797 Fulton Road", address2: nil, city: "Clinton", state: "MD", zip: "20735")
If you want a formatted address against this user, you might do something like this:
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user.address.formatted_address
However, this doesn’t look good and requires more writing than necessary. Here’s where delegate comes in. Go ahead and try it to see the magic.
In user.rb, add this line:
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delegate :formatted_address, to: :address
Now you can access the formatted address directly from the user object.
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user.formatted_address
There you have it! Happy formatting!