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