CODEWITHSUNDEEP
swiftgenerics
rid
rid

Reputation: 63492

Swift implicit protocol

Is there any way to describe in Swift an IntegerType that has a max property? (something similar to implicit interfaces in go)

There is no protocol to describe a max attribute, and even if I create one, IntegerType does not explicitly implement it.

So basically I'm looking for something like:

class Test<T: IntegerType where ?> { // <- ? = something like 'has a "max: Self"' property
}

let t = Test<UInt8>()

or maybe something like:

implicit protocol IntegerTypeWithMax: IntegerType {
    static var max: Self { get }
}

class Test<T: IntegerTypeWithMax> {
}

let t = Test<UInt8>()

Upvotes: 2

Views: 698

Answers (1)

Martin R
Martin R

Reputation: 539815

The Swift compiler does not automatically infer protocol conformance even if a type implements all the required properties/methods. So if you define

protocol IntegerTypeWithMax: IntegerType {
    static var max: Self { get }
}

you still have to make the integer types that you are interested in conform to that protocol:

extension UInt8 : IntegerTypeWithMax { }
extension UInt16 : IntegerTypeWithMax { }
// ...

The extension block is empty because UInt8, UInt16 already have a static max method.

Then

class Test<T: IntegerTypeWithMax> {
}

let t = Test<UInt8>()

compiles and works as expected.

Upvotes: 3

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