158 lines
4.3 KiB
Swift
158 lines
4.3 KiB
Swift
//
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// Binding.swift
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// Meta
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//
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// Created by david-swift on 26.05.24.
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//
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/// A property wrapper for a property of a view that binds the property of the parent view.
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///
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/// ```swift
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/// struct Grandparent: View {
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///
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/// @State private var state = false
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///
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/// var view: Body {
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/// Parent(value: $state)
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/// }
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/// }
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///
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/// struct Parent: View {
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///
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/// @Binding var value: Bool
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///
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/// var view: Body {
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/// Child(value: $value)
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/// }
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///
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/// }
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///
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/// struct Child: View {
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///
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/// @Binding var value: Bool
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///
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/// var view: Body {
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/// // ...
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/// }
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///
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/// }
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/// ```
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@propertyWrapper
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@dynamicMemberLookup
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public struct Binding<Value> {
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/// The value.
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public var wrappedValue: Value {
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get {
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getValue()
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}
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nonmutating set {
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setValue(newValue)
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for handler in handlers {
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handler(newValue)
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}
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}
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}
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/// Get the value as a binding using the `$` prefix.
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public var projectedValue: Binding<Value> {
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.init {
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wrappedValue
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} set: { newValue in
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wrappedValue = newValue
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}
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}
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/// The closure for getting the value.
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private let getValue: () -> Value
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/// The closure for settings the value.
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private let setValue: (Value) -> Void
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/// Handlers observing whether the binding changes.
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private var handlers: [(Value) -> Void] = []
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/// Get a property of any content of a `Binding` as a `Binding`.
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/// - Parameter keyPath: The path to the member.
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/// - Returns: The binding.
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public subscript<Subject>(dynamicMember keyPath: WritableKeyPath<Value, Subject>) -> Binding<Subject> {
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.init {
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wrappedValue[keyPath: keyPath]
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} set: { newValue in
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wrappedValue[keyPath: keyPath] = newValue
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}
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}
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/// Initialize a property that is bound from a parent view.
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/// - Parameters:
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/// - get: The closure for getting the value.
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/// - set: The closure for setting the value.
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public init(get: @escaping () -> Value, set: @escaping (Value) -> Void) {
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self.getValue = get
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self.setValue = set
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}
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/// Initialize a property that does not react to changes in the child view.
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/// - Parameters:
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/// - value: The constant value.
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/// - Returns: The binding.
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public static func constant(_ value: Value) -> Binding<Value> {
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.init {
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value
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} set: { _ in
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}
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}
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/// Observe whether data is changed over this binding.
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/// - Parameter handler: The handler.
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/// - Returns: The binding.
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public func onSet(_ handler: @escaping (Value) -> Void) -> Self {
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var newSelf = self
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newSelf.handlers.append(handler)
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return newSelf
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}
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}
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extension Binding where Value: MutableCollection {
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/// Get a child at a certain index of the array as a binding.
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/// - Parameters:
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/// - index: The child's index.
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/// - defaultValue: The value used if the index is out of range does not exist.
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/// - Returns: The child as a binding.
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public subscript(safe index: Value.Index?, default defaultValue: Value.Element) -> Binding<Value.Element> {
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.init {
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if let index, wrappedValue.indices.contains(index) {
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return wrappedValue[index]
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}
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return defaultValue
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} set: { newValue in
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if let index, wrappedValue.indices.contains(index) {
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wrappedValue[index] = newValue
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}
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}
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}
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}
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extension Binding where Value: MutableCollection, Value.Element: Identifiable {
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/// Get a child of the array with a certain id as a binding.
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/// - Parameters:
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/// - id: The child's id.
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/// - defaultValue: The value used if the index is out of range does not exist.
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/// - Returns: The child as a binding.
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public subscript(id id: Value.Element.ID?, default defaultValue: Value.Element) -> Binding<Value.Element> {
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self[safe: wrappedValue.firstIndex { $0.id == id }, default: defaultValue]
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}
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}
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extension Binding: CustomStringConvertible where Value: CustomStringConvertible {
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/// A textual description of the wrapped value.
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public var description: String {
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wrappedValue.description
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}
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}
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