Question

我对Array的扩展有问题，我试图添加一个方法来检测是否有任何重复，如果我使它成为一个全局函数它可以工作，但是，当我尝试使它成为一个抱怨的Array扩展中的方法：

extension Array {
    static func hasDuplicates<T:Hashable>(array:Array<T>) -> Bool {
        var map = Dictionary<T,Bool>()

        for var x = 0; x < array.count; x++ {
            let currentItem = array[x] as T
            if map[currentItem] {
                return true
            } else {
                map[currentItem] = true
            }
        }
        return false
    }
}

func hasDuplicates<T:Hashable>(array:Array<T>) -> Bool {
    var map = Dictionary<T,Bool>()

    for var x = 0; x < array.count; x++ {
        let currentItem = array[x] as T
        if map[currentItem] {
            return true
        } else {
            map[currentItem] = true
        }
    }
    return false
}

func testDuplicates() {
    var arrayWithDuplicates = [ "not repeated", "is repeated", "not repeated again", "repeated", "this isn't repeated", "repeated", "is repeated" ]
    var arrayWithoutDuplicates = [ "not repeated", "not repeated again","this isn't repeated", "isn't repeated" ]

    XCTAssert(hasDuplicates(arrayWithDuplicates), "There ARE duplicates")
    XCTAssert(hasDuplicates(arrayWithoutDuplicates) == false, "There AREN'T any duplicates")

    // Shows an error: Cannot convert the expression's type 'Void' to type 'String'        
    XCTAssert(Array.hasDuplicates(arrayWithDuplicates), "There ARE duplicates")
    XCTAssert(Array.hasDuplicates(arrayWithoutDuplicates) == false, "There AREN'T any duplicates")
}

我做错了什么？或者它是XCode中的错误？

Answer 1

如果没有指定通用参数，则不能将Array用作类型：

替换：

Array.hasDuplicates(arrayWithDuplicates)

与

Array<String>.hasDuplicates(arrayWithDuplicates)

Swift：使用类型函数扩展数组并不起作用

1 个答案: