CODEWITHSUNDEEP
ruby-on-railsforms
tim_xyz
tim_xyz

Reputation: 13481

What is `delegate` in a Rails form object file?

I have a ruby form object, xForm that inherits from Form.

class xForm < Form
  # code
end

There is a section inside the form file called # Delegations

delegate :id, :xyz,
         :email, :email=,
         ...
         to: :user

I haven't dealt with form objects or delegations before, and wasn't able to find information by searching Google.

Can anyone explain what they are used for on a high-level?

Upvotes: 1

Views: 754

Answers (1)

Taryn East
Taryn East

Reputation: 27747

Delegate is used if you want to easily access a value on an associated object

In your example, your Form has a user. In order to access email, you could continually type: my_form.user.email or you could use delegation (as in your example) which means you can just type my_form.email and the form figures out where to get the email from.

It allows you to reduce typing, but also to hide away implementation-details.

http://apidock.com/rails/Module/delegate explains it pretty well if you want more

Typically this is used for Form objects so that you can build a flatter params-structure in the view that contains the form. eg if you delegate both :email and :email= then you can name a field :email in the my_form form... and then in the controller you can just use my_form = MyForm.new(params[:my_form]) instead of having to separately instantiate the associated objects and pass the attributes specific to each.

Upvotes: 3

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