Hi,
In order not to make an unnecessary crowd here, first I tried to learn
it myself, but I failed.
What is that “super” method? Could someone explain it please?
Thanks in advance.
On Thu, 2006-02-02 at 18:03 +0900, Rubyist wrote:
What is that “super” method? Could someone explain it please?
The ‘super’ commentary starts below. This is just a base-class.
class SomeClass
def initialize(one, two, three)
puts “Some: #{[one, two, three].inspect}”
end
def ameth(one)
“Some:ameth: #{one}”
end
end
1. When you override a method, you don’t ever have to consider the
inherited method if you don’t want to.
class OtherClass < SomeClass
def initialize(*args)
puts “Other: #{args.inspect}”
end
end
2. Sometimes, though, you’ll want to invoke the inherited method,
e.g. to make sure any initialization gets done. For this you
use the ‘super’ keyword, which says 'invoke the inherited method
of this name’. Without args, super passes this method’s arguments
to the superclass method.
class FurtherClass < SomeClass
def initialize(*args)
super
puts “Further: #{args.inspect}”
end
end
3. If you’re changing interfaces (with initialize) you might want to
pass up different arguments, which you can do by passing them
to super.
class LastClass < SomeClass
def initialize(a1,a2)
puts “Last: #{[a1,a2].inspect}”
super(a1,a2,3)
end
3.5. You can of course get the result from super and massage it
as you need to when overriding methods.
def ameth(one)
s = super(‘ten’)
“Last:ameth:#{s}”
end
end
4. You don’t have to use super. This is mostly equivalent from
the user point of view (don’t know about internally).
class Alternative < SomeClass
alias :__old_init :initialize
def initialize(one,two)
__old_init(one,two, 3)
puts “Alternative: #{[one, two].inspect}”
end
end
SomeClass.new(1,2,3)
=> Some: [1, 2, 3]
OtherClass.new(1,2,3)
=> Other: [1, 2, 3]
FurtherClass.new(1,2,3)
=> Some: [1, 2, 3]
=> Further: [1, 2, 3]
l = LastClass.new(:one, :two)
=> Last: [:one, :two]
=> Some: [:one, :two, 3]
puts l.ameth(55)
=> Last:ameth:Some:ameth: ten
Alternative.new(10,20)
=> Some: [10, 20, 3]
=> Alternative: [10, 20]
There’s probably more stuff I forgot, but thats the basic gist of it.