选择器上的选择器

Question

所以我试图在用户选择选择器选项后运行一个函数。

这个想法是用户可以设置一个默认站，所以我需要能够将选择的值发送到一个函数，这样我就可以将它保存在核心数据模块中。

我想知道是否有人知道如何做到这一点。

import SwiftUI

struct SettingsView: View {
    var frameworks = ["DRN1", "DRN1 Hits", "DRN1 United", "DRN1 Life"]
    @State private var selectedFrameworkIndex = 0
    
    func doSomethingWith(value: String) {
        print(value)
    }
    
    var body: some View {
        NavigationView {
            Form {
                Section {
                    Picker(selection: $selectedFrameworkIndex, label: Text("Favorite Station")) {
                        ForEach(0 ..< frameworks.count) {
                            Text(self.frameworks[$0])
                        }
                    }.onReceive([self.frameworks].publisher.first()) { value in
                        self.doSomethingWith(value: value)
                    }
                }
            }
            .navigationBarTitle("Settings")
        }
    }
}

Answer 1

不要使用onRecive，而是尝试使用onChange。

您的代码：

.onReceive([self.frameworks].publisher.first()) { value in
    self.doSomethingWith(value: value)
}

更正：

.onChange(of: $selectedFrameworkIndex, perform: { value in
        self.doSomethingWith(value: value)
    })

这将在每次更改 $selectedFrameworkIndex 时触发。

Answer 2

我会在选择器上使用一个简单的.onChange(of:) 调用。它将了解@State var 的变化并允许您对其采取行动。像这样使用它：

import SwiftUI

struct SettingsView: View {
   var frameworks = ["DRN1", "DRN1 Hits", "DRN1 United", "DRN1 Life"]
   @State private var selectedFrameworkIndex = 0

    
    func doSomethingWith(value: String) {
            print(value)
      }
    
   var body: some View {
    NavigationView {
            Form {
                Section {
                    Picker(selection: $selectedFrameworkIndex, label: Text("Favorite Station")) {
                        ForEach(0 ..< frameworks.count) {
                            Text(self.frameworks[$0])
                        }
                    }
                     // Put your function call in here:
                     .onChange(of: selectedFrameworkIndex) { value in
                        print(value)
                    }

                    }
                }
            }
            .navigationBarTitle("Settings")
        }
   }


}

Answer 3

你的：

import SwiftUI

struct SettingsView: View {
   var frameworks = ["DRN1", "DRN1 Hits", "DRN1 United", "DRN1 Life"]
   @State private var selectedFrameworkIndex = 0
   
   func doSomethingWith(value: String) {
       print(value)
   }
    
   var body: some View {
    NavigationView {
            Form {
                Section {
                    Picker(selection: $selectedFrameworkIndex, label: Text("Favorite Station")) {
                        ForEach(0 ..< frameworks.count) {
                            Text(self.frameworks[$0])
                        }
                    }.onReceive([self.frameworks].publisher.first()) { value in
                        self.doSomethingWith(value: value)
                    }
                }
            }
            .navigationBarTitle("Settings")
        }
   }


}

添加一个变量来检查 selectedFrameworkIndex 是否已更改。 改变：

import SwiftUI

struct SettingsView: View {
    var frameworks = ["DRN1", "DRN1 Hits", "DRN1 United", "DRN1 Life"]
    @State private var selectedFrameworkIndex = 0
    @State private var savedFrameworkIndex = 0
    
   func handler<Value: Any>(val: Value) -> Value {
       if selectedFrameworkIndex != savedFrameworkIndex {
           self.doSomethingWith(value: self.frameworks[selectedFrameworkIndex])
       }
       return val
   }

    func doSomethingWith(value: String) {
        print(value)
    }
    var body: some View {
        NavigationView {
            Form {
                Section {
                    Picker(selection: handler(val: $selectedFrameworkIndex), label: Text("Favorite Station")) {
                        ForEach(0 ..< frameworks.count) {
                            Text(self.frameworks[$0])
                        }
                    }
                }
            }
            .navigationBarTitle("Settings")
        }
    }
}