FormattingTextField

FormattingTextField is a SwiftUI text input component that applies a formatting rule before publishing changes to your model.

Unlike the common TextField + onChange approach (where the raw value is written first and corrected afterwards), this component uses an internal input buffer. The user edits a local @State string, the input is processed through a transformation closure, and only the processed result is written to the external @Binding.

This guarantees that observers (e.g. @Published with didSet, validation logic, or side effects) never receive intermediate unformatted values. It is especially useful when the text drives logic such as validation, networking, or state transitions.

Typical use cases include:

• limiting input length
• trimming whitespace
• allowing digits only
• normalizing separators and casing
• applying any custom text transformation without noisy intermediate updates

struct ContentView: View {
    @State var vm: ViewModel = .init()
    
    var body: some View {
        FormattingTextField("Name", text: $vm.name) {
            String($0.prefix(30))
        }
    }
}

Read more here:

https://livsycode.com/swiftui/how-to-avoid-double-updates-when-filtering-swiftui-textfield-input/