使结构化Hashable？ [英] Make struct Hashable?

问题描述

我正在尝试创建排序的字典 [petInfo：UIImage]（）但是我收到错误类型'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其变为哈希，但是它的任何组件都不是一个整数是什么 var hashValue：Int 需要。如果没有一个字段是整数，怎么使它符合协议？我可以使用 dbName ，如果我知道这个结构的所有出现将是唯一的？

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 。 FYI - 哈希值不一定是唯一的。要求是等于等于的两个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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