Add conveniences for working with optional bindings and alerts

Author: stackotter

Sources/SwiftCrossUI/State/Binding.swift

@@ -2,12 +2,12 @@
 /// as a writable reference to the value.
 @dynamicMemberLookup
 @propertyWrapper
-public class Binding<Value> {
+public struct Binding<Value> {
     public var wrappedValue: Value {
         get {
             getValue()
         }
-        set {
+        nonmutating set {
             setValue(newValue)
         }
     }
@@ -32,6 +32,21 @@ public class Binding<Value> {
         self.setValue = set
     }
 
+    public init?(_ other: Binding<Value?>) {
+        if let initialValue = other.wrappedValue {
+            self.init(
+                get: {
+                    other.wrappedValue ?? initialValue
+                },
+                set: { newValue in
+                    other.wrappedValue = newValue
+                }
+            )
+        } else {
+            return nil
+        }
+    }
+
     /// Projects a property of a binding.
     public subscript<T>(dynamicMember keyPath: WritableKeyPath<Value, T>) -> Binding<T> {
         get {

Sources/SwiftCrossUI/State/State.swift

@@ -28,6 +28,10 @@ public struct State<Value>: DynamicProperty, StateProperty {
             /// setting a new value. This isn't in a didSet property accessor
             /// because we want more granular control over when it does and
             /// doesn't trigger.
+            ///
+            /// Additionally updates the downstream observation if the
+            /// wrapped value is an Optional<some ObservableObject> and the
+            /// current case has toggled.
             func postSet() {
                 // If the wrapped value is an Optional<some ObservableObject>
                 // then we need to observe/unobserve whenever the optional

Sources/SwiftCrossUI/Views/Modifiers/AlertModifier.swift

@@ -11,6 +11,24 @@ extension View {
             actions: actions()
         )
     }
+
+    public func alert(
+        _ title: Binding<String?>,
+        @AlertActionsBuilder actions: () -> [AlertAction]
+    ) -> some View {
+        AlertModifierView(
+            child: self,
+            title: title.wrappedValue ?? "",
+            isPresented: Binding {
+                title.wrappedValue != nil
+            } set: { newValue in
+                if !newValue {
+                    title.wrappedValue = nil
+                }
+            },
+            actions: actions()
+        )
+    }
 }
 
 struct AlertModifierView<Child: View>: TypeSafeView {

Sources/SwiftCrossUI/Views/Slider.swift

@@ -104,11 +104,10 @@ public struct Slider: ElementaryView, View {
                 maximum: maximum,
                 decimalPlaces: decimalPlaces,
                 environment: environment
-            ) { [weak value] newValue in
-                guard let value = value else {
-                    return
+            ) { newValue in
+                if let value {
+                    value.wrappedValue = newValue
                 }
-                value.wrappedValue = newValue
             }
 
             if let value = value?.wrappedValue {