I have class Foo, and I overload two of its methods == and eql?:
class Foo
def initialize(bar)
@bar = bar
end
def bar
@bar
end
def ==(o)
self.bar == o.bar
end
def .eql?(o)
return ==(o)
end
end
I test that f1 and f2 below are equal with respect to the two methods:
u = User.find(12345)
f1 = Foo.new(u)
f2 = Foo.new(u)
f1 == f2 # => true
f1.eql?(f2) # => true
But Hash#has_key? does not render them equal:
{f1 => true}.has_key?(f2) # => false
What is the equality method used in Hash#has_key??
Most implementations of a hash type, Ruby’s included, rely on a hash first (for speed!) and then equality checks. To verify that it works, first, you can just add
def hash
1
end
After that, you should work on providing as many possible distinct return values for hash that will still be equal if the objects are considered equal (as long as it’s fast, of course).
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