[英]How to observe a TextField value with SwiftUI and Combine?
I'm trying to execute an action every time a textField
's value is changed.每次更改
textField
的值时,我都会尝试执行一个操作。
@Published var value: String = ""
var body: some View {
$value.sink { (val) in
print(val)
}
return TextField($value)
}
But I get below error.但我得到以下错误。
Cannot convert value of type 'Published' to expected argument type 'Binding'
无法将“已发布”类型的值转换为预期的参数类型“绑定”
This should be a non-fragile way of doing it:这应该是一种非脆弱的方式:
class MyData: ObservableObject {
var value: String = "" {
willSet(newValue) {
print(newValue)
}
}
}
struct ContentView: View {
@ObservedObject var data = MyData()
var body: some View {
TextField("Input:", text: $data.value)
}
}
In your code, $value
is a publisher, while TextField
requires a binding.在您的代码中,
$value
是一个发布者,而TextField
需要一个绑定。 While you can change from @Published
to @State
or even @Binding
, that can't observe the event when the value is changed.虽然您可以从
@Published
更改为@State
甚至@Binding
,但是当值更改时无法观察到事件。
It seems like there is no way to observe a binding.似乎没有办法观察绑定。
An alternative is to use ObservableObject
to wrap your value type, then observe the publisher ( $value
).另一种方法是使用
ObservableObject
来包装您的值类型,然后观察发布者 ( $value
)。
class MyValue: ObservableObject {
@Published var value: String = ""
init() {
$value.sink { ... }
}
}
Then in your view, you have have the binding $viewModel.value
.然后在您看来,您拥有绑定
$viewModel.value
。
struct ContentView: View {
@ObservedObject var viewModel = MyValue()
var body: some View {
TextField($viewModel.value)
}
}
I don't use combine for this.我不为此使用组合。 This it's working for me:
这对我有用:
TextField("write your answer here...",
text: Binding(
get: {
return self.query
},
set: { (newValue) in
self.fetch(query: newValue) // any action you need
return self.query = newValue
}
)
)
I have to say it's not my idea, I read it in this blog: SwiftUI binding: A very simple trick我不得不说这不是我的想法,我在这个博客中读到了它: SwiftUI binding:一个非常简单的技巧
如果你想观察value
那么它应该是一个State
@State var value: String = ""
You can observe TextField
value by using ways,您可以通过使用方法观察
TextField
值,
import SwiftUI
import Combine
struct ContentView: View {
@State private var Text1 = ""
@State private var Text2 = ""
@ObservedObject var viewModel = ObserveTextFieldValue()
var body: some View {
//MARK: TextField with Closures
TextField("Enter text1", text: $Text1){
editing in
print(editing)
}onCommit: {
print("Committed")
}
//MARK: .onChange Modifier
TextField("Enter text2", text: $Text2).onChange(of: Text2){
text in
print(text)
}
//MARK: ViewModel & Publisher(Combine)
TextField("Enter text3", text: $viewModel.value)
}
}
class ObserveTextFieldValue: ObservableObject {
@Published var value: String = ""
private var cancellables = Set<AnyCancellable>()
init() {
$value.sink(receiveValue: {
val in
print(val)
}).store(in: &cancellables)
}
}
@Published is one of the most useful property wrappers in SwiftUI, allowing us to create observable objects that automatically announce when changes occur that means whenever an object with a property marked @Published is changed, all views using that object will be reloaded to reflect those changes. @Published 是 SwiftUI 中最有用的属性包装器之一,它允许我们创建可观察对象,这些对象会在发生更改时自动通知,这意味着每当带有标记为 @Published 的属性的 object 发生更改时,使用该 ZA8CFDE6331BD59EB2AC96F891 的所有视图都将被重新加载到那些变化。
import SwiftUI
struct ContentView: View {
@ObservedObject var textfieldData = TextfieldData()
var body: some View {
TextField("Input:", text: $textfieldData.data)
}
}
class TextfieldData: ObservableObject{
@Published var data: String = ""
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
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