swift - 错误 : Cannot subscript a value of 'Dictionary with an index of type ' Int64'

Question

var dict = Dictionary<Int64, ExternalInfo>()

为上面的字典创建一个扩展名

extension Dictionary where Key: IntegerLiteralConvertible, Value: ExternalInfo {

    func contains(id: Int64) -> Bool {
        return self[id] != nil
        /* return self[3] != nil */ // No issue
    }

    mutating func remove(id: Int64) {
        removeValueForKey(id)
    }
}

它会为这两个语句抛出一些编译器级别的错误。需要做什么？？

Cannot subscript a value of 'Dictionary with an index of type 'Int64'

Answer 1

尝试使用SignedIntegerType代替IntegerLiteralConvertible，这是不同整数类型之间更好的通用协议(protocol):

extension Dictionary where Key: SignedIntegerType, Value: ExternalInfo {

    func contains(id: Int64) -> Bool {
        return self[Key(id)] != nil
    }

    mutating func remove(id: Int64) {
        removeValueForKey(Key(id))
    }
}