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Swift的combineframework combinelatetest的问题

swift5.1 swift ios

Allen Savio · 技术社区 · 5 年前

我浏览了WWDC的“介绍Combine”视频,视频中说每当发布者的值被更新时,combineTest就会被调用和更新。但我创建的代码片段工作起来很奇怪。

class Mango {
    var enableButton = false
    @Published var userName = "admin"
    @Published var password = "poweruser"
    @Published var passwordAgain = "poweruser"
    var validatePassword: AnyCancellable {
        Publishers.CombineLatest($password, $passwordAgain).map { (password, reenterpass) -> String? in
            print("Is Password Same to \(password)? :", password == reenterpass)
            guard password == reenterpass else { return nil }
            return password
        }.eraseToAnyPublisher()
            .map { (str) -> Bool in
            print("In Map", str != nil)
            guard str != nil else { return false }
            return true
        }.assign(to: \.enableButton, on: self)
    }

    init() {
        validatePassword
    }

    func checkSub() {
        print("1. Is password same? ->",enableButton)
        password = "nopoweruser"
        print("2. Is password same? ->",enableButton)
    }
}

当我初始化并调用更新发布者“password”的checkSub()函数时,不会调用combineTest。为什么它的行为很奇怪?

输入:

let mango = Mango()<br>
mango.checkSub()

输出:

Is Password Same to poweruser? : true  
In Map true  
1. Is password same? -> true  
2. Is password same? -> true

0 回复 | 直到 5 年前

Sandeep 5 年前

似乎问题出在内存管理上。这个 validatePassword lazy var 它应该很好用。

lazy var validatePassword: AnyCancellable = {
    Publishers.CombineLatest($password, $passwordAgain).map { (password, reenterpass) -> String? in
        print("Is Password Same to \(password)? :", password == reenterpass)
        guard password == reenterpass else { return nil }
        return password
    }.eraseToAnyPublisher()
        .map { (str) -> Bool in
        print("In Map", str != nil)
        guard str != nil else { return false }
        return true
    }.assign(to: \.enableButton, on: self)
}()

与 lazy 您将保留只有在对象被释放之后才被释放的cancelable。所以,这应该能正常工作。