Reputation: 569
Recently, i am reading "functional programming in swift". In the book, the author does some extension of Int to meet a protocol Smaller
. In order to get a thorough understanding of the author's idea, i copy the code to my own playground, but it reports error.
protocol Smaller {
static func smaller() -> Self?
}
extension Int: Smaller {
static func smaller() -> Int? {
//reporting error: Binary operator "==" cann't be applied to type of Int.type and Int
return self == 0 ? nil : self / 2
}
}
it seems that self == 0
is not allowed in the extension. Does anybody have an idea of the reason.
Upvotes: 4
Views: 111
Reputation: 955
I don't think you wanted to use a static function as you need a instantiated integer to work on and check if it is smaller.
So there are 2 approaches:
Remove the static from the function and then call it normally:
let aInt = 4
aInt.smaller() //will be 2
or you change the signature of the static function to accept the instance as an argument
`
protocol Smaller {
static func smaller(selfToMakeSmall: Self) -> Self?
}
extension Int: Smaller {
static func smaller(selfToMakeSmall: Int) -> Int? {
//reporting error: Binary operator "==" cann't be applied to type of Int.type and Int
return selfToMakeSmall == 0 ? nil : selfToMakeSmall / 2
}
}
let theInt = 4
Int.smaller(theInt)
`
but I think this could be also improved with Generics
Upvotes: 1