CODEWITHSUNDEEP
ruby
Jon Schneider
Jon Schneider

Reputation: 26973

Ruby: Alias unexpectedly points to parent class implementation of the aliased method?

I have the following Ruby code that features an alias in a child class of a method that's defined in the superclass, and overridden in the child class:

class Parent
  def hello
    print "Hello, I'm Parent!"
  end
end

class Child < Parent
  alias greet hello
  def hello
    print "Hi, I'm Child!"
  end
end

When I call the greet alias on an instance of Child, it calls the Parent implementation of hello, not its own class's implementation. For example, with the above code loaded in irb:

2.3.3 :001 > child = Child.new
 => #<Child:0x007fb1118a8f58> 
2.3.3 :002 > child.hello
Hi, I'm Child! => nil 
2.3.3 :003 > child.greet
Hello, I'm Parent! => nil 
2.3.3 :004 >

How can I get the alias to point to the local implementation of the method instead of the parent class implementation?

Upvotes: 1

Views: 71

Answers (1)

Jon Schneider
Jon Schneider

Reputation: 26973

The alias needs to be located after the method to be aliased, not before.

This revised code for the Child class will have greet aliased to the local implementation of hello, as intended:

class Child < Parent
  def hello
    print "Hi, I'm Child!"
  end
  alias greet hello
end

Upvotes: 2

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