CODEWITHSUNDEEP
ruby-on-railsruby
Andy
Andy

Reputation: 751

What is the meaning of using attr_reader in rails a helper module?

module ProductsHelper
  attr_reader :products, :product    
end

What is the outcome of doing the above? I saw this in Rails guide, and just don't understand.

Upvotes: 2

Views: 1609

Answers (2)

engineerDave
engineerDave

Reputation: 3935

This is a Ruby convention which creates a "getter" called product and another called products.

For example if you had an object ph which is equivalent to ProductHelper.new. 

ph = ProductHelper.new

And within that module there exists an instance variable. 

def initialize
  @products = "awesomeness"
end

You wouldn't be able to access it without doing a send on the module as it would be considered private to that instance of ph.

(Don't worry if the following is confusing as its not something you'll see much as a newcomer to rails. You'll see it more when you get into meta programming.) 

ProductsHelper.send :products

However an attr_reader would allow you to read the method or variable as if it were an attribute of the instance. 

ProductHelper.products

It essentially does this piece of code for you. 

def products
  @products # which is an instance variable within the instantiated object.
end

Although you'll usually only see these in your model classes not in Modules ... since all classes in Ruby are modules though, this behavior exists at that level too. If you don't have any methods then would return information then calling .products would only return nil.

In Ruby, there are also attr_writers which create "setters" too. 

def products( value )
  @products = value
end

Which allow you to do this.

ph.products = "some awesome thing"

Lastly you also have the attr_accessor which creates both a getter and setter in one action.

Upvotes: 3

Krists
Krists

Reputation: 451

It will allow to read values from @products and @product instance variables by calling products and product in the view. You still need to set them in controller.

These readers dont realy do much of a help.

Upvotes: 2

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