无法使用类型（，）的参数列表调用[Method]

I have two protocols A and B where B inherits from A.

我有两个协议A和B,其中B继承自A.

protocol A { }

protocol B: A { }

And I have a utility class which has function called add whose parameter should conform to the protocol A:

我有一个实用程序类,其函数名为add,其参数应符合协议A:

class Utility {
    func add<T:A>(t:T.Type,param:T){
        ....
    }
}

Then I have a test class which creates object of Utility and calls its function add which accepts a parameter of type B (class object which implements B):

然后我有一个测试类,它创建Utility的对象并调用它的函数add,它接受一个B类参数(实现B的类对象):

class Test {
    var util: Utility

    init() {
        util = Utility()
    }

    func addItem(data:B){
        util.add(B.self,param: data) // This line produces Cannot invoke add with argument list 
    }                         // of type (B.Protocol,param:B)
}

What am I doing wrong?

我究竟做错了什么?

1 个解决方案

#1

Your mistake is that you are trying to accept variable as a protocol, not the type conforming to the protocol:

你的错误是你试图接受变量作为协议,而不是符合协议的类型:

func addItem(data:B){
    util.add(B.self,param: data)
} 

Which is strange, because you did it right in the Utility class. Simple fix is to do exactly the same here (using constraints):

这很奇怪,因为你在Utility类中做得很好。简单的解决方法是在这里完全相同(使用约束):

func addItem<T: B>(data: T) {
    util.add(T.self, param: data)
}