Swift version: 5.6
This might sound obvious, but protocol extensions are extensions to protocols as opposed to concrete types. For example, the BinaryInteger
protocol is adopted by all integer types: Int
, Int64
, UInt8
, and so on. If you wanted to add a method to all of those at once, you’d use a protocol extension to modify BinaryInteger
, like this:
extension BinaryInteger {
func cubed() -> Self {
return self * self * self
}
}
That cubed()
method will now existing on all integer types, so you can write code like this:
let i: Int = 5
let j: UInt8 = 7
print(i.cubed())
print(j.cubed())
Note: Self
with a capital S refers to whatever type conforms to the protocol, e.g. Int
or UInt32
, whereas self
with a lowercase S refers to whatever the current value of the type is, e.g. 5 or 99.
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