如何检查 SwiftUI 何时订阅了 ObservableObject 的已发布属性？

Posted 2023-02-24

【中文标题】如何检查 SwiftUI 何时订阅了 ObservableObject 的已发布属性？

【英文标题】：How to check when SwiftUI subscribed to published property of ObservableObject?

【发布时间】：2020-05-21 12:59:37

【问题描述】：

我这样做了，但从未调用 print 语句。我错过了什么？

final class TestObservableObject: ObservableObject 
    @Published
    private (set) var publishedProperty: Int = 0
    var objectWillChange: AnyPublisher<Int, Never>? = Empty().eraseToAnyPublisher()
    init() 
        self.objectWillChange = $publishedProperty.handleEvents(receiveSubscription:  (_) in
            print("receiveSubscription")
        ).eraseToAnyPublisher()
    


struct TestView: View 
    @ObservedObject
    private var test: TestObservableObject
    init() 
        test = TestObservableObject()
    
    var body: some View 
        return Group 
            if test.publishedProperty == 0 
                Text("0")
             else 
                Text("100")
            
        
    

【参考方案1】：

啊，只是换了

var objectWillChange: AnyPublisher<Int, Never>?

到

var objectWillChange: AnyPublisher<Int, Never>

工作。