&tag(SwiftUI/PropertyWrapper);
struct StateSample: View {
private var counter = 0
var body: some View {
Button(action: {
self.counter += 1
}, label: {
Text("counter is \(counter)")
})
}
}
struct ParentView: View {
@State private var counter = 0
var body: some View {
ChildView(counter: $counter)
.frame(width: .infinity)
}
}
struct ChildView: View {
@Binding var counter: Int
var body: some View {
Button(action: {
counter += 1
}, label: {
Text("\(counter)")
.font(.title)
})
.border(Color.red)
}
}
struct EnvironmentSample: View {
@Environment(\.colorScheme) var colorScheme: ColorScheme
var body: some View {
if colorScheme == .dark {
Text("dark mode")
} else if colorScheme == .light {
Text("light mode")
} else {
Text("")
}
}
}
class DataSource: ObservableObject {
@Published var counter = 0
}
struct StateObjectSample: View {
@StateObject private var dataSource = DataSource()
var body: some View {
VStack {
Button("increment counter") {
dataSource.counter += 1
}
Text("StateObject count: \(dataSource.counter)")
.font(.title)
}
}
}
fileprivate
struct ParentView: View {
@StateObject private var dataSource = DataSource()
var body: some View {
ChildView(dataSource: dataSource)
}
}
fileprivate
struct ChildView: View {
@ObservedObject var dataSource: DataSource
var body: some View {
VStack {
Button("increment counter") {
dataSource.counter += 1
}
Text("count: \(dataSource.counter)")
}
}
}
}
}
** @StateObjectと@ObservedObjectの違い
-以下のサンプルを考える。
#pre{{
struct StateObjectCounterView: View {
@StateObject private var dataSource = DataSource()
var body: some View {
VStack {
Button("increment counter") {
dataSource.counter += 1
}
Text("StateObject count: \(dataSource.counter)")
.font(.title)
}
}
}
struct ObservedObjcetCounterView: View {
@ObservedObject private var dataSource = DataSource()
var body: some View {
VStack {
Button("increment counter") {
dataSource.counter += 1
}
Text("ObservedObject count: \(dataSource.counter)")
.font(.title)
}
}
}
struct SwitchColorView: View {
@State private var isDanger: Bool = false
var body: some View {
VStack {
Button("Change the Color") {
isDanger.toggle()
}
if isDanger {
Circle().foregroundColor(.red)
.frame(width: 200, height: 200)
} else {
Circle().foregroundColor(.green)
.frame(width: 200, height: 200)
}
StateObjectCounterView()
ObservedObjcetCounterView()
Spacer()
}
}
}
fileprivate
struct ParentView: View {
var body: some View {
ChildView()
}
}
fileprivate
struct ChildView: View {
var body: some View {
GrandChildView()
}
}
fileprivate
struct GrandChildView: View {
@EnvironmentObject var dataSource: DataSource
var body: some View {
Text("\(dataSource.counter)")
}
}
struct EnvironmentObjectSample_Previews: PreviewProvider {
@StateObject static private var dataSource = DataSource()
static var previews: some View {
ParentView().environmentObject(dataSource)
}
}