字典扩展返回组合字典 [英] Dictionary extension to return a combined dictionary

问题描述

我正在以下列方式扩展Swift的字典类：

I'm trying to extend Swift's dictionary class in the following manner:

extension Dictionary {

    func merge<K, V>(dict: [K:V]) -> Dictionary<K, V> {
        var combinedDict: [K:V] = [:]
        for (k, v) in self {
            combinedDict[k] = v
        }

        for (k, v) in dict {
            combinedDict[k] = v
        }

        return combinedDict
    }



}

第一个for循环给了我错误：can not subscript类型为'[K：V]'的类型为'Key'的值，但第二个for循环很好。我甚至评论了第一个检查，第二个仍然工作。任何人知道问题是什么？谢谢！

The first for loop gives me the error: "Cannot subscript a value of type '[K:V]' with an index of type 'Key'" but the second for loop is fine. I even commented out the first one to check and the second still works. Anyone know what the problem is? Thanks!

推荐答案

字典类型已定义 Key 和 Value 作为通用变量，因此不需要$（code> K 和 V 导致问题）。

The dictionary type already defines Key and Value as generic variables, so K and V are not required (and cause the problem).

extension Dictionary {
    func merge(dict: [Key : Value]) -> [Key : Value] {
        var combinedDict = self

        for (k, v) in dict {
            combinedDict[k] = v
        }

        return combinedDict
    }
}

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