使用SwiftUI将TextField限制为x个字符

问题描述

使用iOS13.2，Swift-5.1.2，Xcode-11.2，我尝试以下操作:

Using iOS13.2, Swift-5.1.2, Xcode-11.2, I try the following:

我想使用一个TextField.用户只能在文本字段中输入x个字符.

I want to use a TextField. The user shall only be able to enter x-amount of characters into the TextField.

我的代码如下:

import Combine
import SwiftUI

class Entry: ObservableObject {

  @Published var entry = "" {
    didSet {
        entry = String(entry.prefix(6)) // trying to limit to 6 characters
    }
  }
}

在上面的代码中，已经有例外行.

And in the above code, there is already the exception line.

我可以看到 didSet {...} 是错误的(因为我们最终一次又一次地处于无穷循环设置/didSetting中)...

I can see that the didSet{...} is wrong (since we end up in an endless loop setting/didSetting again and again)...

将TextField限制为x个字符的更好方法是什么?

这是其余的代码:

struct NumberView: View {
    var body: some View {

        Group {
            HStack {
                Spacer()
                NumberIcon(number: 1)
                NumberIcon(number: 2)
                NumberIcon(number: 3)
                NumberIcon(number: 4)
                NumberIcon(number: 5)
                NumberIcon(number: 6)
                Spacer()
            }
         }
    }
}

struct NumberIcon: View {
    @ObservedObject private var entry = Entry()
    var number: Int = 0
    var body: some View {
        TextField(" ", text: $entry.entry, onEditingChanged: { editing in
            print(editing)
            print(self.$entry)
        })
            .padding()
            .foregroundColor(Color.black)
            .background(Color.green)
            .font(.largeTitle)
            .lineLimit(1)
            .cornerRadius(16.0)
            .clipped()
            .keyboardType(.numberPad)
    }
}

struct NumberView_Previews: PreviewProvider {
    static var previews: some View {
        NumberView()
    }
}

我知道有UIKit包装器可以使用UITextFieldDelegate形式的老式 shouldChangeCharactersIn 委托方法-但我想纯粹通过SwiftUI(无UIKit代码)实现字符限制.我该怎么办?

I know that there are UIKit wrapper possibilities to use the good-old shouldChangeCharactersIn delegate methods form UITextFieldDelegate - but I would like to implement the character limitation purely with SwiftUI (no UIKit code). How can I do that ?

推荐答案

在SwiftUI中实现此目的的最简单方法是在达到最大字符数时禁用TextField:

The easiest way to achive this in SwiftUI is just to disable the TextField when the maximum number of characters is reached:

struct LimittedTextField: View {

    @State private var entry = ""

    let characterLimit = 6

    var body: some View {
        TextField("", text: $entry)
            .disabled(entry.count > (characterLimit - 1))
    }
}

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