swift - 带有hashValue的“Expression was too complex to be solved in reasonable time…”

Question

试图使我的整个数据模型可哈希化，例如...

let id:Int
let projectID:Int
let parentID:Int
let name:String
let description:String
let url:String
let startOn:Date?
let startedOn:Date?
let dueOn:Date?
let completedOn:Date?
let isStarted:Bool
let isCompleted:Bool

var hashValue:Int
{
    return (31 &* id.hashValue)
            &+ projectID.hashValue
            &+ parentID.hashValue
            &+ name.hashValue
            &+ description.hashValue
            &+ url.hashValue
            &+ (startOn != nil ? startOn!.hashValue: 0)
            &+ (startedOn != nil ? startedOn!.hashValue: 0)
            &+ (dueOn != nil ? dueOn!.hashValue: 0)
            &+ (completedOn != nil ? completedOn!.hashValue: 0)
            &+ isStarted.hashValue
            &+ isCompleted.hashValue
}

我得到编译错误:

Error:(112, 5) expression was too complex to be solved in reasonable time; consider breaking up the expression into distinct sub-expressions

因此，出现了一个问题:在哈希取决于许多属性的情况下，如何使对象可哈希化？我有一些模型对象，其数量是上述属性的3-4倍。

Answer 1

将您的表情分成多部分，并通过添加下一个添加项来添加所有这些表达

var hashValue:Int
    {
        let firstFrg =  (31 &* id.hashValue)
                &+ projectID.hashValue
                &+ parentID.hashValue
                &+ name.hashValue
        let secondFrg = firstFrg + &+ description.hashValue
                &+ url.hashValue
                &+ (startOn != nil ? startOn!.hashValue: 0)
        let thirdFrg = secondFrg + &+ (startedOn != nil ? startedOn!.hashValue: 0)
                &+ (dueOn != nil ? dueOn!.hashValue: 0)
                &+ (completedOn != nil ? completedOn!.hashValue: 0)
        let fourthFrg = thirdFrg + &+ isStarted.hashValue
                &+ isCompleted.hashValue

         return fourthFrg
    }