不能专门化非通用定义

Question

I have tried following Cannot explicitly specialize a generic function and I can't get a hold of this

This is my code

class A<T>{
    func test(){
        self.verify(value : T.self)
    }
    
    func verify<T>(value: T) {
        print("Default")
    }
}

extension A where T == String {
    func verify<T>(value: T){
        print("Str")
    }
}



let o = A<String>()
o.test()

The test is the only available function that can be called. When I'm executing this, I get Default not Str.

But according to the generics, I should get Str. What am I doing wrong here? What should I do to keep extension A give me Str if T == String

Answer 1

Ok, so I'm learning generics new here. And this is what I got,

class A<T>{
     func test(){
        print("Def Test")
     
        verifyVal()
    }
    
    func verify() {
        print("Default verifyVal")
    }
}

extension A where T == String {
    func test(){
        print("String")
    }
}
extension A where T == Int {
    func test(){
        print("Int")
    }
}



let o = A<String>()
o.test()

let a = A<Int>()
a.test()

This will give you the expected result

String
Int

So basically overload the test method instead of verify. However, there are some caveats

1. If the method test is inherited from another class, say A is a child of N where the method test was originally written, there is no way you can override it in the extensions.

Thats it.