new vs. initialize

[Jeff Davis]

If MyClass.new calls the initialize method, what calls the new method?
What if both are defined?

Thanks,
Jeff Davis

 

[Mark Hubbart]

Hi,

If MyClass.new calls the initialize method, what calls the new method?
What if both are defined?

*You* call the new method. It's pre-defined in Class to work something
like this:

class Class
def new
obj = self.allocate # allocates the object
obj.initialize # calls the object's initialize method
return obj # returns the object
end
end

You can redefine new to do anything you want, remembering that people
will expect it to return an object of that class.

cheers,
Mark

 

[Eric Hodel]

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If MyClass.new calls the initialize method, what calls the new method?
What if both are defined?

You call the new method on a Class when you want a new instance of that
class.
The class calls #initialize to set up the instance for you.

Here's how the two tie together in Ruby, expressed as Ruby code.

class MyClass
def self.new(*args, &block) # class method
puts "called MyClass.new"
obj = allocate
# #initialize is a private method, so we use send to invoke it.
obj.send :initialize, *args, &block
return obj
end

def initialize # instance method
puts "called MyClass#initialize"
end
end

p MyClass.new

# => called MyClass.new
# => called MyClass#initialize
# => #<MyClass:0x13356c>


--
Eric Hodel - (e-mail address removed) - http://segment7.net
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