[英]Changing A Picker to a TextField in SwiftUI
我是一個自學 iOS 開發的新手(Paul Hudson 的 100DaysOfSwiftUI,項目 1),目前我遇到了一個我還沒有解決的問題。 最初,numberOfPeople 部分有一個帶有以下代碼的選擇器,我試圖將其更改為文本字段。 首先將其 @State 屬性 (@State private var numberOfPeople = 2) 從 2 更改為空字符串,並嘗試為人數創建另一個計算屬性。 當人數文本字段留空時,當我運行項目時,模擬器上每人數量部分的默認值不會顯示為 0,而是顯示為 NaN,如下面的屏幕截圖所示。 (這讓我想知道 numberOfPeople 是否通過如下 nil 合並成功轉換為 Integer)。 只有當我在人數文本字段中輸入值時,項目才能正常運行。 我不是 100% 確定我哪里出錯了,但是任何幫助都將不勝感激!
struct ContentView: View {
@State private var checkAmount = ""
@State private var numberOfPeople = ""
@State private var tipPercentage = 2
let tipPercentages = [10,15,20,25,0]
let allPeople = 2...100
var totalPerPerson: Double {
let peopleCount = Double(numberOfPeople) ?? 0
let tipSelection = Double(tipPercentages[tipPercentage])
let orderAmount = Double(checkAmount) ?? 0
let tipValue = orderAmount / 100 * tipSelection
let grandTotal = orderAmount + tipValue
let amountPerPerson = grandTotal / peopleCount
return amountPerPerson
}
var grandTotal: Double {
let tipSelection = Double(tipPercentages[tipPercentage])
let orderAmount = Double(checkAmount) ?? 0
let tipValue = orderAmount / 100 * tipSelection
let totalAmount = orderAmount + tipValue
return totalAmount
}
var body: some View {
NavigationView {
Form {
Section {
TextField("Amount", text: $checkAmount)
.keyboardType(.decimalPad)
TextField("Number of people", text: $numberOfPeople)
.keyboardType(.numberPad)
}
Section(header: Text("How much tip do you want to leave?")) {
Picker("Tip percentage", selection: $tipPercentage) {
ForEach(0 ..< tipPercentages.count) {
Text("\(self.tipPercentages[$0])%")
}
}
.pickerStyle(SegmentedPickerStyle())
}
Section (header: Text("Total Amount")){
Text("$\(grandTotal, specifier: "%.2f")")
}
Section (header: Text("Amount Per Person")){
Text("$\(totalPerPerson, specifier: "%.2f")")
}
}
.navigationBarTitle("WeSplit")
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
(Original code for picker)
Picker("Number of people", selection: $numberOfPeople) {
ForEach(2 ..< 100) {
Text("\($0) people")
(Original code for people count)
let peopleCount = Double(numberOfPeople + 2)
你看到的是試圖除以零的結果。 如果在使用以下方法進行除法之前, peopleCount
為0
,則可以通過從totalPerPerson
function 返回0
來避免該計算:
var totalPerPerson: Double {
let peopleCount = Double(numberOfPeople) ?? 0
let tipSelection = Double(tipPercentages[tipPercentage])
let orderAmount = Double(checkAmount) ?? 0
guard peopleCount > 0 else {
return 0
}
let tipValue = orderAmount / 100 * tipSelection
let grandTotal = orderAmount + tipValue
let amountPerPerson = grandTotal / peopleCount
return amountPerPerson
}
請記住,使用新的TextField
,而不是選擇器,即使您指定.decimalPad
或.numberPad
,用戶仍然可以在這些字段中輸入非數字值,因此您可能想要輸入如果發生這種情況,則會出現錯誤(或者,在 SO 上搜索有關僅接受數字的字段的解決方案)。 此解決方案中指定了此類 TextField 的示例
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