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September 10, 2024 11:53
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PropertyWrapper: @transaction binding for SwiftUI to make changes to data supporting commit/rollback
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struct User: Equatable { | |
var firstName: String | |
var lastName: String | |
} | |
@main | |
struct MyApp: App { | |
@State var value = User(firstName: "", lastName: "") | |
@State var showEdit = false | |
var body: some Scene { | |
WindowGroup { | |
VStack { | |
Text("First Name: \(value.firstName)") | |
Text("Last Name: \(value.lastName)") | |
Button("Edit") { showEdit = true } | |
} | |
.sheet(isPresented: $showEdit) { | |
UserEditView(value: $value.transaction()) | |
} | |
} | |
} | |
} | |
struct UserEditView: View { | |
@Transaction var value: User | |
var body: some View { | |
VStack { | |
TextField("First Name", text: $value.firstName) | |
TextField("Last Name", text: $value.lastName) | |
Divider() | |
Button("Commit", action: $value.commit).disabled(!$value.hasChanges) | |
Button("Rollback", action: $value.rollback).disabled(!$value.hasChanges) | |
} | |
} | |
} |
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@main | |
struct MyApp: App { | |
@State var value = 0 | |
var body: some Scene { | |
WindowGroup { | |
MyView(value: $value.transaction()) | |
} | |
} | |
} | |
struct MyView: View { | |
@Transaction var value: Int | |
var body: some View { | |
VStack { | |
Text("Value: \(value)") | |
Text("HasChanges: \($value.hasChanges ? "yes" : "no")") | |
Divider() | |
Button("Increase") { value += 1 } | |
Button("Commit", action: $value.commit) | |
Button("Rollback", action: $value.rollback) | |
} | |
} | |
} |
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import SwiftUI | |
@propertyWrapper | |
@dynamicMemberLookup | |
public struct Transaction<Value>: DynamicProperty { | |
@State private var derived: Value | |
@Binding private var source: Value | |
fileprivate init(source: Binding<Value>) { | |
self._source = source | |
self._derived = State(wrappedValue: source.wrappedValue) | |
} | |
public var wrappedValue: Value { | |
get { derived } | |
nonmutating set { derived = newValue } | |
} | |
public var projectedValue: Transaction<Value> { self } | |
public subscript<T>(dynamicMember keyPath: WritableKeyPath<Value, T>) -> Binding<T> { | |
return $derived[dynamicMember: keyPath] | |
} | |
public var binding: Binding<Value> { $derived } | |
public func commit() { | |
source = derived | |
} | |
public func rollback() { | |
derived = source | |
} | |
} | |
extension Transaction where Value: Equatable { | |
public var hasChanges: Bool { return source != derived } | |
} | |
extension Binding { | |
public func transaction() -> Transaction<Value> { .init(source: self) } | |
} |
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hey @agisilaos , currently this requires you base the transaction off a
Binding
so you should be able to do something like:if you want to provide just a value you could do something like
then you can do
but this would be a detached object, commits don't propagate anywhere (which is fine for previews)