如何处理 swiftui @State 可选解包 [英] how to deal with swiftui @State optional unwrap

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本文介绍了如何处理 swiftui @State 可选解包的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

在 swiftui 中,我有一个状态变量 count ,它是可选的,在当前的工作表中,我解开可选并显示 Detailview,但它似乎从未出现过.

in swiftui, I have a state variable count ,which is optional, in the sheet present ,I unwrap the optional and show Detailview, but it seems never hit there.

知道为什么不去那里吗?

any idea how why not hit there?

它似乎从未命中

DetailView(count: num)

DetailView(count: num)

     import SwiftUI
        struct ContentView: View {
            @State var showDetailView = false
           @State var count : Int?
        var testArr = [1,2,3,4,5]
        var body: some View {
            
            NavigationView {
                List(testArr.indices){ indice in
                    Text("row num \(indice)")
                        .onTapGesture{
                            
                            self.showDetailView = true
                            self.count = 5
                            }
                    
                    }
                    .sheet(isPresented: self.$showDetailView) {
                    
                        if let num = self.count{
                            
                        //never hit here
                        DetailView(count: num)
                        }
                    
                    }
                
                    .navigationBarTitle("Your Reading")
            }
            }
        }
    
        struct ContentView_Previews: PreviewProvider {
            static var previews: some View {
                ContentView()
            }
        }
    
    struct DetailView: View {
    
        var count: Int
    
        var body: some View {
                if count == 5 {
                     Text("5555")
                } else {
                    EmptyView()
                }
    
             }
        }

推荐答案

你可以使用 sheet(item:content:) 而不是 sheet(isPresented:content:):

You can use sheet(item:content:) instead of sheet(isPresented:content:):

struct ContentView: View {
    @State var count: Int?
    var testArr = [1, 2, 3, 4, 5]

    var body: some View {
        NavigationView {
            List(testArr.indices) { index in
                Text("row num \(index)")
                    .onTapGesture {
                        self.count = 5
                    }
            }
            .sheet(item: $count) { count in
                DetailView(count: count)
            }
            .navigationBarTitle("Your Reading")
        }
    }
}

注意item必须符合Identifiable,所以要么使用自己的struct,要么创建一个Int扩展:

Note that item must conform to Identifiable, so you need to either use your own struct or create an Int extension:

extension Int: Identifiable {
    public var id: Int { self }
}

这篇关于如何处理 swiftui @State 可选解包的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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