您可以这样做:
protocol SomeProtocol {
func someMethodInSomeProtocol()
}
class SomeType { }
class SomeOtherType: SomeType, SomeProtocol {
func someMethodInSomeProtocol() { }
}
class SomeOtherOtherType: SomeType, SomeProtocol {
func someMethodInSomeProtocol() { }
}
func someMethod<T: SomeType where T: SomeProtocol>(condition: Bool) -> T {
var someVar : T
if (condition) {
someVar = SomeOtherType() as T
}
else {
someVar = SomeOtherOtherType() as T
}
someVar.someMethodInSomeProtocol()
return someVar as T
}
这定义了一个函数,该函数返回类型为“SomeType”和协议“SomeProtocol”的对象,并返回符合这些条件的对象。