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dictionarytuplesswift

In Swift can I use a tuple as the key in a dictionary?

I'm wondering if I can somehow use an x, y pair as the key to my dictionary

let activeSquares = Dictionary <(x: Int, y: Int), SKShapeNode>()

But I get the error:

Cannot convert the expression's type '<<error type>>' to type '$T1'

and the error:

Type '(x: Int, y: Int)?' does not conform to protocol 'Hashable'

So.. how can we make it conform?

Solution

  • The definition for Dictionary is struct Dictionary<KeyType : Hashable, ValueType> : ..., i.e. the type of the key must conform to the protocol Hashable. But the language guide tells us that protocols can be adopted by classes, structs and enums, i.e. not by tuples. Therefore, tuples cannot be used as Dictionary keys.

    A workaround would be defining a hashable struct type containing two Ints (or whatever you want to put in your tuple).