I'd like to write an extension for tuples of (e.g.) two value in Swift. For instance, I'd like to write this swap
method:
let t = (1, "one")
let s = t.swap
such that s
would be of type (String, Int)
with value ("one", 1)
. (I know I can very easily implement a swap(t)
function instead, but that's not what I'm interested in.)
Can I do this? I cannot seem to write the proper type name in the extension
declaration.
Additionally, and I suppose the answer is the same, can I make a 2-tuple adopt a given protocol?
A tuple's values can have different types, and you can change their values, provided it's declared as mutable with var. But, after initialization, you can't add any more items to it.
The reason that tuples cannot be used as keys (or specifically, are not hashable ) is because they are not strictly immutable.
But you can't use the contains() method: a. contains((3, 4)) // no!
You can create tuples from as many values as you want and from any number of different data types.
You cannot extend tuple types in Swift. According to Types, there are named types (which can be extended) and compound types. Tuples and functions are compound types.
See also (emphasis added):
Extensions
Extensions add new functionality to an existing class, structure, or enumeration type.
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