使结构可哈希? [英] Make struct Hashable?

问题描述

我正在尝试创建 [petInfo : UIImage]() 类型的字典，但我收到错误 Type 'petInfo' 不符合协议 'Hashable'.我的 petInfo 结构是这样的:

I'm trying to create a dictionary of the sort [petInfo : UIImage]() but I'm getting the error Type 'petInfo' does not conform to protocol 'Hashable'. My petInfo struct is this:

struct petInfo {
    var petName: String
    var dbName: String
}

所以我想以某种方式使它可散列，但它的任何组件都不是整数，这正是 var hashValue: Int 所要求的.如果它的所有字段都不是整数，我如何使其符合协议?如果我知道 dbName 对于此结构的所有出现都是唯一的，我可以使用它吗?

So I want to somehow make it hashable but none of its components are an integer which is what the var hashValue: Int requires. How can I make it conform to the protocol if none of its fields are integers? Can I use the dbName if I know it's going to be unique for all occurrences of this struct?

推荐答案

只需从 hashValue 函数返回 dbName.hashValue.仅供参考 - 哈希值不需要是唯一的.要求是两个相等的对象也必须具有相同的哈希值.

Simply return dbName.hashValue from your hashValue function. FYI - the hash value does not need to be unique. The requirement is that two objects that equate equal must also have the same hash value.

struct PetInfo: Hashable {
    var petName: String
    var dbName: String

    var hashValue: Int {
        return dbName.hashValue
    }

    static func == (lhs: PetInfo, rhs: PetInfo) -> Bool {
        return lhs.dbName == rhs.dbName && lhs.petName == rhs.petName
    }
}

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