How To Fill Out Cm-010 For Name Change

How to run some code when state changes using onChange()

Paul Hudson @twostraws September 3rd 2021

Updated for Xcode thirteen.ii

SwiftUI lets united states of america attach an onChange() modifier to whatever view, which volition run code of our choosing when some land changes in our program. This is of import, because we tin't always use property observers like didSet with something like @Country.

For case, this volition print proper noun changes as they are typed:

          struct ContentView: View {     @Land private var name = ""      var body: some View {         TextField("Enter your proper name:", text: $proper name)             .textFieldStyle(.roundedBorder)             .onChange(of: name) { newValue in                 print("Proper name changed to \(name)!")             }     } }

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Important: If yous're using Xcode 12 you demand to utilise RoundedBorderTextFieldStyle() rather than .roundedBorder.

Personally, I adopt to add a custom extension to Bounden then that I attach observing lawmaking direct to the binding rather than to the view – it lets me place the observer side by side to the thing it's observing, rather than having lots of onChange() modifiers attached elsewhere in my view.

So, I would use code similar this:

          extension Binding {     func onChange(_ handler: @escaping (Value) -> Void) -> Bounden<Value> {         Binding(             get: { cocky.wrappedValue },             set: { newValue in                 self.wrappedValue = newValue                 handler(newValue)             }         )     } }  struct ContentView: View {     @Land private var name = ""      var body: some View {         TextField("Enter your name:", text: $name.onChange(nameChanged))             .textFieldStyle(.roundedBorder)     }      func nameChanged(to value: String) {         print("Proper noun changed to \(name)!")     } }

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