How to extend an array of a specific type?

Question

Created Jun ’15

Replies 2

Boosts 0

Views 3.8k

Participants 3

How can I extend an Array<UInt8> so that I can access its elements as UInt8 in the extending function? I tried extension Array<UInt8> {} which gives the error message that constraints must be specified in a where clause, but doesn't tell where and how that where clause has to be.

Boost

Answer 1

Jens OP

Jun ’15

And you can't simply use a [UInt8] array, like so:

let byteArray: [UInt8] = [0, 127, 255]
let secondByte = byteArray[1] // secondByte will be of type UInt8
print(secondByte.dynamicType) // Swift.UInt8

?

Otherwise, you can do:

extension Array where T: UnsignedIntegerType {
   ...
}

But you can't do:

extension Array where T == UInt8 {
}

So you have to do this:

extension CollectionType where Generator.Element == UInt8 {
    subscript (position: Self.Index) -> UInt8 {
        return self[position]
    }
}

which is nothing but reimplementing what is already there for all CollectionTypes with UInt8 elements ... So I can't really understand why you're not simply using a [UInt8] array as it already gives you the ability to "access its elements as UInt8".

EDIT: Oh, I understand what you meant, seing Wallacy's answer and rereading your question.

0

Answer 2

Wallacy OP

Jun ’15

extension SequenceType where Generator.Element == UInt8 {
    func someMessage(){
        print("UInt8 Array")
    }
}

let a = [UInt8]();
a.someMessage();

0