TextField for integer

Question

我尝试过使用write a表单，其中有一个文本字段要求用户输入数字。然而，我发现即使用户将数字从0更改为另一个值，比如10 ，它也总是0

struct AddRecordView: View {
@State private var age = 0
var body: some View {
Form {
Section {
HStack {
Text("Age")
Spacer()
TextField("age", value: $age, formatter: NumberFormatter()).multilineTextAlignment(.trailing)
.keyboardType(.numberPad)
}
}
}.toolbar {
ToolbarItem(placement: .navigationBarTrailing) {
Button("Add") {
print("(self.age)") // always 0 here?
}
}
}

Answer 1

不使用数字格式化程序，只需使用Binding来获取和设置您的年龄值：

TextField("age", text: Binding(get: { String(age) }, set: { age = Int($0) ?? 0 }))
.keyboardType(.numberPad)

如果你想在文本字段中只接受整数并限制年龄范围，你需要实现一个文本绑定管理器来控制文本字段的内容：

---

class TextBindingManager: ObservableObject {
@Published var string: String = ""
init(string: String) { self.string = string }
}

---

import SwiftUI
struct ContentView: View {
@ObservedObject private var bindingManager = TextBindingManager(string: "")
@State private var ageString = ""
@State private var age = 0
private let range = 1...123  // you can restrict the age range here
var body: some View {
NavigationView {
Form {
Section {
HStack {
Text("Age")
Spacer()
TextField("age", text: $bindingManager.string)
.keyboardType(.numberPad)
.onChange(of: bindingManager.string) { newValue in
guard !bindingManager.string.isEmpty else {
age = 0
return
}
bindingManager.string.removeAll(where: .isDigit.negated)
guard let newValue = Int(bindingManager.string),
range ~= newValue
else {
if let digit = bindingManager.string.last?.wholeNumberValue {
age = digit
bindingManager.string = String(digit)
ageString = bindingManager.string
return
}
bindingManager.string = ageString
ageString = bindingManager.string
return
}
age = newValue
bindingManager.string = String(newValue)
ageString = bindingManager.string
}
}
}
}
.toolbar {
ToolbarItem(placement: .navigationBarTrailing) {
Button("Add") {
print(age)
}
.disabled(!(range ~= age))
}
}
}
}
}

---

struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

extension Character {
var isDigit: Bool { "0"..."9" ~= self }
}

---

extension Bool {
var negated: Bool { !self }
}