我有一个围绕一些对象的包装类,我想用它作为哈希中的键.包装和解包对象应映射到同一个键.
一个简单的例子是：
class A
attr_reader :x
def initialize(inner)
@inner=inner
end
def x; @inner.x; end
def ==(other)
@inner.x==other.x
end
end
a = A.new(o) #o is just any object that allows o.x
b = A.new(o)
h = {a=>5}
p h[a] #5
p h[b] #nil,should be 5
p h[o] #nil,should be 5
我试过==,===,eq？哈希都无济于事.
解决方法
Hash uses key.eql? to test keys for equality. If you need to use
instances of your own classes as keys in a Hash,it is recommended
that you define both the eql? and hash methods. The hash method must
have the property that a.eql?(b) implies a.hash == b.hash.
所以…
class A
attr_reader :x
def initialize(inner)
@inner=inner
end
def x; @inner.x; end
def ==(other)
@inner.x==other.x
end
def eql?(other)
self == other
end
def hash
x.hash
end
end