objective-c - 如何在 objective c 中使用具有泛型类型的 swift 类

Question

我有以下带有 NumericType T 的 swift 类。

@objc class MathStatistics<T: NumericType> : NSObject {
        var numbers = [T]()

        func sum() -> T? {
            if numbers.count == 0 {
                return nil
            }

            var sum = T(0)

            for value in numbers {
                sum = sum + value
            }
            return sum
        }
    }

在 swift 中初始化类对象如下:

let statistics = MathStatistics<Double>()

如何在 Objective C 中初始化同一个对象？下面这行没有设置数字类型T。

MathStatistics *stats = [[MathStatistics alloc] init];

Answer 1

你不能。如 documentation 中所列:

You’ll have access to anything within a class or protocol that’smarked with the @objc attribute as long as it’s compatible withObjective-C. This excludes Swift-only features such as those listedhere:

• Generics
• Tuples
• Enumerations defined in Swift
• Structures defined in Swift
• Top-level functions defined in Swift
• Global variables defined in Swift
• Typealiases defined in Swift
• Swift-style variadics
• Nested types
• Curried functions

您必须在类里面摆脱泛型。然后就可以在 Objective-C 中使用了