在HackingwithSwift上有一个简单的教程，显示了如何实现UITextView。可以很容易地将其修改为UITextField。

这是一个简单的示例，显示了如何UIViewRepresentable为您使用UITextField。在文本和占位符上设置字距调整。

struct ContentView: View {

    @State var text = ""

    var body: some View {
        MyTextField(text: $text,placeholder: "Placeholder")
    }

}

struct MyTextField: UIViewRepresentable {
    @Binding var text: String
    var placeholder: String

    func makeUIView(context: Context) -> UITextField {
        return UITextField()
    }

    func updateUIView(_ uiView: UITextField,context: Context) {
        uiView.attributedPlaceholder = NSAttributedString(string: self.placeholder,attributes: [
            NSAttributedString.Key.kern: 0.3
        ])
        uiView.attributedText = NSAttributedString(string: self.text,attributes: [
            NSAttributedString.Key.kern: 0.3
        ])
    }
}

更新

以上内容不适用于对attributedText设置字距调整。借用Costantino Pistagna在他的medium article中所做的出色工作，我们需要做更多的工作。

首先，我们需要创建UITextField的包装版本，以允许我们访问委托方法。

class WrappableTextField: UITextField,UITextFieldDelegate {
    var textFieldChangedHandler: ((String)->Void)?
    var onCommitHandler: (()->Void)?

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if let nextField = textField.superview?.superview?.viewWithTag(textField.tag + 1) as? UITextField {
            nextField.becomeFirstResponder()
        } else {
            textField.resignFirstResponder()
        }
        return false
    }

    func textField(_ textField: UITextField,shouldChangeCharactersIn range: NSRange,replacementString string: String) -> Bool {
        if let currentValue = textField.text as NSString? {
            let proposedValue = currentValue.replacingCharacters(in: range,with: string)
            print(proposedValue)
            self.attributedText = NSAttributedString(string: currentValue as String,attributes: [
                NSAttributedString.Key.kern: 10
            ])
            textFieldChangedHandler?(proposedValue as String)
        }
        return true
    }

    func textFieldDidEndEditing(_ textField: UITextField) {
        onCommitHandler?()
    }
}

由于每次文本更改时都会调用shouldChangeCharactersIn委托方法，因此我们应该使用该方法来更新attributedText的值。我尝试先使用proposedVale，但是它将字符加倍，如果我们使用currentValue

现在我们可以在WrappedTextField中使用UIViewRepresentable。

struct SATextField: UIViewRepresentable {
    private let tmpView = WrappableTextField()

    //var exposed to SwiftUI object init
    var tag:Int = 0
    var placeholder:String?
    var changeHandler:((String)->Void)?
    var onCommitHandler:(()->Void)?

    func makeUIView(context: UIViewRepresentableContext<SATextField>) -> WrappableTextField {
        tmpView.tag = tag
        tmpView.delegate = tmpView
        tmpView.placeholder = placeholder
        tmpView.attributedPlaceholder = NSAttributedString(string: self.placeholder ?? "",attributes: [
            NSAttributedString.Key.kern: 10
        ])
        tmpView.onCommitHandler = onCommitHandler
        tmpView.textFieldChangedHandler = changeHandler
        return tmpView
    }

    func updateUIView(_ uiView: WrappableTextField,context: UIViewRepresentableContext<SATextField>) {
        uiView.setContentHuggingPriority(.defaultHigh,for: .vertical)
        uiView.setContentHuggingPriority(.defaultLow,for: .horizontal)
    }
}

我们在makeUIView中设置占位符的属性文本。占位符文本未更新，因此我们不必担心更改它。

这是我们的用法：

struct ContentView: View {

    @State var text = ""

    var body: some View {
        SATextField(tag: 0,placeholder: "Placeholder",changeHandler: { (newText) in
            self.text = newText
        }) {
            // do something when the editing of this textfield ends
        }
    }
}