/Swift/Detect binding valu change swiftui

Detect binding valu change swiftui

import Combine
import SwiftUI

/// See `View.onChange(of: value, perform: action)` for more information
struct ChangeObserver<Base: View, Value: Equatable>: View {
    let base: Base
    let value: Value
    let action: (Value)->Void

    let model = Model()

    var body: some View {
        if model.update(value: value) {
            DispatchQueue.main.async { self.action(self.value) }
        }
        return base
    }

    class Model {
        private var savedValue: Value?
        func update(value: Value) -> Bool {
            guard value != savedValue else { return false }
            savedValue = value
            return true
        }
    }
}

extension View {
    /// Adds a modifier for this view that fires an action when a specific value changes.
    ///
    /// You can use `onChange` to trigger a side effect as the result of a value changing, such as an Environment key or a Binding.
    ///
    /// `onChange` is called on the main thread. Avoid performing long-running tasks on the main thread. If you need to perform a long-running task in response to value changing, you should dispatch to a background queue.
    ///
    /// The new value is passed into the closure. The previous value may be captured by the closure to compare it to the new value. For example, in the following code example, PlayerView passes both the old and new values to the model.
    ///
    /// ```
    /// struct PlayerView : View {
    ///   var episode: Episode
    ///   @State private var playState: PlayState
    ///
    ///   var body: some View {
    ///     VStack {
    ///       Text(episode.title)
    ///       Text(episode.showTitle)
    ///       PlayButton(playState: $playState)
    ///     }
    ///   }
    ///   .onChange(of: playState) { [playState] newState in
    ///     model.playStateDidChange(from: playState, to: newState)
    ///   }
    /// }
    /// ```
    ///
    /// - Parameters:
    ///   - value: The value to check against when determining whether to run the closure.
    ///   - action: A closure to run when the value changes.
    ///   - newValue: The new value that failed the comparison check.
    /// - Returns: A modified version of this view
    func onChange<Value: Equatable>(of value: Value, perform action: @escaping (_ newValue: Value)->Void) -> ChangeObserver<Self, Value> {
        ChangeObserver(base: self, value: value, action: action)
    }
}

Source: stackoverflow.com

Detect binding valu change swiftui

struct TypewriterTextView: View {
    @Binding var textString:String
    @State private var typingInterval = 0.3
    @State private var typedString = ""

    var body: some View {
        Text(typedString).onChange(of: textString) {
            typedString = ""
            Timer.scheduledTimer(withTimeInterval: self.typingInterval, repeats: true, block: { timer in

                if self.typedString.length < self.textString.length {
                    self.typedString = self.typedString + self.textString[self.typedString.length]
                }
                else { timer.invalidate() }
            })
        }
    }
}

Source: stackoverflow.com

Similar codes

0 vote157 views1 answer
Method overloading
Swift
-1 vote187 views1 answer
Most frequent element in array swift
Swift
0 vote165 views1 answer
Swiftui change form section color
Swift
0 vote152 views1 answer
Swift hide button
Swift
0 vote110 views1 answer
How to get dictonary key and value swift
Swift
0 vote174 views1 answer
Swift check if class is of type
Swift
0 vote154 views1 answer
Url encode xcode
Swift
1 vote215 views1 answer
Swift bring something to front of view
Swift
1 vote180 views1 answer
CoreData line of code
Swift
0 vote155 views1 answer
Xcode collapse cpde shortcut
Swift