Question

我有一个协议CustomObject，并且为String添加了扩展以符合CustomObject。我还为Array（如果Element转换为CustomObject和Dictionary（如果键和值符合CustomObject）添加了条件一致性。但是，当我尝试将包含String和CustomObject的数组分配给CustomObject变量（或作为参数传递时，编译器会抱怨为Value of type '[CustomObject]' does not conform to specified type 'CustomObject'

在条件符合数组的情况下，如果元素为CustomObject，则数组也应为CustomObject。

这缺少什么？

尝试的代码：

protocol CustomObject {
    var value: String { get }
}

extension String: CustomObject {
    var value: String {
        return self
    }
}

extension Array: CustomObject where Element: CustomObject {
    var value: String {
        return "{\n\(self.map{$0.value}.joined(separator: "\n"))\n}"
    }
}

extension Dictionary: CustomObject where Key: CustomObject, Value: CustomObject {
    var value: String {
        return self.map {
            return "\($0.value){\n\($1.value)\n}"
            }
            .joined(separator: "\n")
    }
}


var params = [
    "v1",
    "v2",
]
let dict1 = ["key1": params]
let dict2: CustomObject = ["key2": dict1]
let array1: CustomObject = ["key3", dict2.value]// Error here `Value of type '[CustomObject]' does not conform to specified type 'CustomObject'`


func doSomething(_ object: CustomObject) {
    //...
    print("value -- " + object.value)
}

let array2 = ["key3", dict2]
doSomething(array2)// Here also `Value of type '[CustomObject]' does not conform to specified type 'CustomObject'`

更新：

如果我将数组扩展名更改为extension Array: CustomObject where Element == CustomObject，则该错误将消失，并出现另一个错误。

let dict2: CustomObject = ["key2": dict1]//Contextual type 'CustomObject' cannot be used with dictionary literal

条件一致性数组协议无法识别

0 个答案: