我创建了一个自定义文本字段，我想利用Combine。为了在文本字段中的文本更改时得到通知，我目前使用自定义修饰符。它工作正常，但我希望此代码可以在CustomTextField结构中使用。
我的CustomTextField结构符合UIViewRepresentable。在此结构中，有一个名为Coordinator的NSObject类，它符合UITextFieldDelegate。
我已经在使用其他UITextField委托方法，但是找不到与我的自定义修饰符完全一样的方法。一些方法很接近，但是并没有完全按照我希望的方式表现。无论如何，我觉得最好将此新的自定义textFieldDidChange方法放在Coordinator类中。
这是我的自定义修饰符
private let textFieldDidChange = NotificationCenter.default
.publisher(for: UITextField.textDidChangeNotification)
.map { $0.object as! UITextField}
struct CustomModifer: ViewModifier {
func body(content: Content) -> some View {
content
.tag(1)
.onReceive(textFieldDidChange) { data in
//do something
}
}
}
我的CustomTextField用于SwiftUI视图，并附加了我的自定义修饰符。只要文本字段发生更改，我就可以执行操作。修改器还使用Combine。它很好用，但是我不希望此功能采用修饰符的形式。我想在Coordinator类中使用它，以及UITextFieldDelegate方法。
这是我的CustomTextField
struct CustomTextField: UIViewRepresentable {
var isFirstResponder: Bool = false
@EnvironmentObject var authenticationViewModel: AuthenticationViewModel
func makeCoordinator() -> Coordinator {
return Coordinator(authenticationViewModel: self._authenticationViewModel)
}
class Coordinator: NSObject, UITextFieldDelegate {
var didBecomeFirstResponder = false
@EnvironmentObject var authenticationViewModel: AuthenticationViewModel
init(authenticationViewModel: EnvironmentObject<AuthenticationViewModel>)
{
self._authenticationViewModel = authenticationViewModel
}
// Limit the amount of characters that can be typed in the field
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
let currentText = textField.text ?? ""
guard let stringRange = Range(range, in: currentText) else { return false }
let updatedText = currentText.replacingCharacters(in: stringRange, with: string)
return updatedText.count <= 14
}
/* I want to put my textFieldDidChange method right here */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * */
func textFieldDidEndEditing(_ textField: UITextField) {
textField.resignFirstResponder()
textField.endEditing(true)
}
}
func makeUIView(context: Context) -> UITextField {
let textField = UITextField()
textField.delegate = context.coordinator
textField.placeholder = context.coordinator.authenticationViewModel.placeholder
textField.font = .systemFont(ofSize: 33, weight: .bold)
textField.keyboardType = .numberPad
return textField
}
func updateUIView(_ uiView: UITextField, context: Context) {
let textField = uiView
textField.text = self.authenticationViewModel.text
}
}
struct CustomTextField_Previews: PreviewProvider {
static var previews: some View {
CustomTextField()
.previewLayout(.fixed(width: 270, height: 55))
.previewDisplayName("Custom Textfield")
.previewDevice(.none)
}
}
我一直在观看有关Combine的视频，我想在我正在开发的新应用中开始使用它。我确实认为在这种情况下使用是正确的做法，但仍然不确定如何实现这一目标。我真的很喜欢一个例子。
总结一下：
我想在我的Coordinator类中添加一个名为textFieldDidChange的函数，并且每次我的文本字段发生更改时都应该触发该函数。它必须利用Combine。
预先感谢
答案 0 :(得分：2)
在查看了您的最新问题之后，我意识到我的原始答案可能需要进行一些清理。我已经将模型和协调器分解为一个类，尽管以我的示例为例，但这并不总是可行或理想的。如果模型和协调器不能相同，则不能依赖模型属性的didSet方法来更新textField。因此，我改为使用我们在模型中使用@Published变量免费获得的Combine发布者。
我们需要做的关键事情是：
通过使model.text和textField.text保持同步，从而使真理成为唯一来源
使用@Published属性包装器提供的发布者在textField.text发生更改时更新model.text
在.addTarget(:action:for)发生更改时，使用textField上的model.text方法来更新textfield.text
在模型更改时执行名为textDidChange的闭包。
（与＃{1}相比，我更喜欢使用.addTarget，而不是经过NotificationCenter，因为它的代码更少，可以立即工作，并且UIKit的用户众所周知）。
以下是显示此工作方式的更新示例：
import SwiftUI
import Combine
// Example view showing that `model.text` and `textField.text`
// stay in sync with one another
struct CustomTextFieldDemo: View {
@ObservedObject var model = Model()
var body: some View {
VStack {
// The model's text can be used as a property
Text("The text is \"\(model.text)\"")
// or as a binding,
TextField(model.placeholder, text: $model.text)
.disableAutocorrection(true)
.padding()
.border(Color.black)
// or the model itself can be passed to a CustomTextField
CustomTextField().environmentObject(model)
.padding()
.border(Color.black)
}
.frame(height: 100)
.padding()
}
}
class Model: ObservableObject {
@Published var text = ""
var placeholder = "Placeholder"
}
struct CustomTextField: UIViewRepresentable {
@EnvironmentObject var model: Model
func makeCoordinator() -> CustomTextField.Coordinator {
Coordinator(model: model)
}
func makeUIView(context: UIViewRepresentableContext<CustomTextField>) -> UITextField {
let textField = UITextField()
// Set the coordinator as the textField's delegate
textField.delegate = context.coordinator
// Set up textField's properties
textField.text = context.coordinator.model.text
textField.placeholder = context.coordinator.model.placeholder
textField.autocorrectionType = .no
// Update model.text when textField.text is changed
textField.addTarget(context.coordinator,
action: #selector(context.coordinator.textFieldDidChange),
for: .editingChanged)
// Update textField.text when model.text is changed
// The map step is there because .assign(to:on:) complains
// if you try to assign a String to textField.text, which is a String?
// Note that assigning textField.text with .assign(to:on:)
// does NOT trigger a UITextField.Event.editingChanged
let sub = context.coordinator.model.$text.receive(on: RunLoop.main)
.map { Optional($0) }
.assign(to: \UITextField.text, on: textField)
context.coordinator.subscribers.append(sub)
// Become first responder
textField.becomeFirstResponder()
return textField
}
func updateUIView(_ textField: UITextField, context: UIViewRepresentableContext<CustomTextField>) {
// If something needs to happen when the view updates
}
}
extension CustomTextField {
class Coordinator: NSObject, UITextFieldDelegate, ObservableObject {
@ObservedObject var model: Model
var subscribers: [AnyCancellable] = []
// Make subscriber which runs textDidChange closure whenever model.text changes
init(model: Model) {
self.model = model
let sub = model.$text.receive(on: RunLoop.main).sink(receiveValue: textDidChange)
subscribers.append(sub)
}
// Cancel subscribers when Coordinator is deinitialized
deinit {
for sub in subscribers {
sub.cancel()
}
}
// Any code that needs to be run when model.text changes
var textDidChange: (String) -> Void = { text in
print("Text changed to \"\(text)\"")
// * * * * * * * * * * //
// Put your code here //
// * * * * * * * * * * //
}
// Update model.text when textField.text is changed
@objc func textFieldDidChange(_ textField: UITextField) {
model.text = textField.text ?? ""
}
// Example UITextFieldDelegate method
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
textField.resignFirstResponder()
return true
}
}
}
听起来您有几个目标：
UITextField，以便您可以使用.becomeFirstResponder()之类的功能我认为您可以使用单个模型类和UIViewRepresentable结构满足所有这些要求。我以这种方式构造代码的原因是，您有一个真实的来源（model.text），可以与其他采用String或Binding<String>的SwiftUI视图互换使用。
class MyTextFieldModel: NSObject, UITextFieldDelegate, ObservableObject {
// Must be weak, so that we don't have a strong reference cycle
weak var textField: UITextField?
// The @Published property wrapper just makes a Combine Publisher for the text
@Published var text: String = "" {
// If the model's text property changes, update the UITextField
didSet {
textField?.text = text
}
}
// If the UITextField's text property changes, update the model
@objc func textFieldDidChange() {
text = textField?.text ?? ""
// Put your code that needs to run on text change here
print("Text changed to \"\(text)\"")
}
// Example UITextFieldDelegate method
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
textField.resignFirstResponder()
return true
}
}
struct MyTextField: UIViewRepresentable {
@ObservedObject var model: MyTextFieldModel
func makeUIView(context: UIViewRepresentableContext<MyTextField>) -> UITextField {
let textField = UITextField()
// Give the model a reference to textField
model.textField = textField
// Set the model as the textField's delegate
textField.delegate = model
// TextField setup
textField.text = model.text
textField.placeholder = "Type in this UITextField"
// Call the model's textFieldDidChange() method on change
textField.addTarget(model, action: #selector(model.textFieldDidChange), for: .editingChanged)
// Become first responder
textField.becomeFirstResponder()
return textField
}
func updateUIView(_ textField: UITextField, context: UIViewRepresentableContext<MyTextField>) {
// If something needs to happen when the view updates
}
}
如果您不需要上面的＃3，则可以替换
@ObservedObject var model: MyTextFieldModel
使用
@ObservedObject private var model = MyTextFieldModel()
这是一个演示视图，显示了所有这些工作
struct MyTextFieldDemo: View {
@ObservedObject var model = MyTextFieldModel()
var body: some View {
VStack {
// The model's text can be used as a property
Text("The text is \"\(model.text)\"")
// or as a binding,
TextField("Type in this TextField", text: $model.text)
.padding()
.border(Color.black)
// but the model itself should only be used for one wrapped UITextField
MyTextField(model: model)
.padding()
.border(Color.black)
}
.frame(height: 100)
// Any view can subscribe to the model's text publisher
.onReceive(model.$text) { text in
print("I received the text \"\(text)\"")
}
}
}
答案 1 :(得分：1)
我还需要在SwiftUI中使用UITextField，所以我尝试了以下代码：
struct MyTextField: UIViewRepresentable {
private var placeholder: String
@Binding private var text: String
private var textField = UITextField()
init(_ placeholder: String, text: Binding<String>) {
self.placeholder = placeholder
self._text = text
}
func makeCoordinator() -> Coordinator {
Coordinator(textField: self.textField, text: self._text)
}
func makeUIView(context: Context) -> UITextField {
textField.placeholder = self.placeholder
textField.font = UIFont.systemFont(ofSize: 20)
return textField
}
func updateUIView(_ uiView: UITextField, context: Context) {
}
class Coordinator: NSObject {
private var dispose = Set<AnyCancellable>()
@Binding var text: String
init(textField: UITextField, text: Binding<String>) {
self._text = text
super.init()
NotificationCenter.default
.publisher(for: UITextField.textDidChangeNotification, object: textField)
.compactMap { $0.object as? UITextField }
.compactMap { $0.text }
.receive(on: RunLoop.main)
.assign(to: \.text, on: self)
.store(in: &dispose)
}
}
}
struct ContentView: View {
@State var text: String = ""
var body: some View {
VStack {
MyTextField("placeholder", text: self.$text).padding()
Text(self.text).foregroundColor(.red).padding()
}
}
}
答案 2 :(得分：0)
我对您的要求有些困惑，因为您是在谈论UITextField和SwiftUI。
这样的事情呢？它不使用UITextField，而是使用SwiftUI的TextField对象。
只要您的TextField中的ContentView发生更改，此类都会通知您。
class CustomModifier: ObservableObject {
var observedValue: String = "" {
willSet(observedValue) {
print(observedValue)
}
}
}
确保您在修饰符类上使用@ObservedObject，并且可以看到更改。
struct ContentView: View {
@ObservedObject var modifier = CustomModifier()
var body: some View {
TextField("Input:", text: $modifier.observedValue)
}
}
如果这与您的要求完全不符，那么我可以建议以下文章，这可能会有所帮助吗？
https://medium.com/@valv0/textfield-and-uiviewrepresentable-46a8d3ec48e2