Added SwiftUI environment helpers

Author: RCCoop

README.md

@@ -17,6 +17,7 @@ Helpful tools for Core Data
         - [ModelManager and ModelFileManager Protocols](#modelmanager-and-modelfilemanager-protocols)
         - [ModelVersion Protocol](#modelversion-protocol)
         - [PersistentHistoryTracker actor](#persistenthistorytracker-actor)
+        - [SwiftUI Integration](#swiftui-integration)
 - [CRUD Helpers](#crud-helpers)
     - [Updatable Protocol](#updatable-protocol)
     - [Persistable Protocol](#persistable-protocol)
@@ -228,6 +229,37 @@ let stack = try BasicDataStack(
 stack.historyTracker?.startMonitoring()
 ```
 
+### SwiftUI Integration
+
+You can add your `DataStack` and its `viewContext` to the SwiftUI environment in a single call:
+
+```swift
+struct MyView: View {
+    var myStack: MyDataStack
+    
+    var body: some View {
+        SubView()
+            .dataStackEnvironment(myStack)
+    }
+}
+```
+
+The `.dataStackEnvironment(_:)` call wraps `.environment(_:,_:)` calls for both the DataStack and ManagedObjectContext, so you can access either environment value with the following property wrappers:
+
+```swift
+struct SubView: View {
+    /// This is a NSManagedObjectContext accessed by `myStack.viewContext`
+    @Environment(\.managedObjectContext) var context
+    
+    /// This is a (any DataStack)? equal to `myStack` from MyView.
+    @EnvironmentDataStack var dataStack
+    
+    var body: some View { ... }
+}
+```
+
+You must set the DataStack into a view's environment using the `dataStackEnvironment(_:)` call in order to use the `@EnvironmentDataStack` property wrapper, or it will cause a fatal error.
+
 # CRUD Helpers
 
 ### Updatable Protocol

Sources/RCDataKit/Data Stack/DataStackProtocol.swift

@@ -6,7 +6,7 @@ import CoreData
 import Foundation
 
 /// A type that provides some standard helper tools for managing a CoreData persistent store.
-public protocol DataStack {
+public protocol DataStack: Sendable {
     /// The `NSPersistentContainer` that the `DataStack` wraps.
     var container: NSPersistentContainer { get }
 

Sources/RCDataKit/Data Stack/Helpers/SwiftUI+DataStack.swift

@@ -0,0 +1,85 @@
+//
+//  SwiftUI+DataStack.swift
+//  RCDataKit
+//
+//  Created by Ryan Linn on 11/10/24.
+//
+
+import SwiftUI
+
+extension View {
+    /// Adds the `DataStack` to the View's environment.
+    ///
+    /// This call includes adding the `DataStack`'s `viewContext` to the View environment, so child views
+    /// can access both or either the `DataStack` and/or `managedObjectContext` through the following
+    /// variable declarations:
+    ///
+    /// ```swift
+    /// struct MyView: View {
+    ///     // Get the DataStack's viewContext:
+    ///     @Environment(\.managedObjectContext) var context
+    ///
+    ///     // Get the DataStack
+    ///     @EnvironmentDataStack var dataStack
+    /// }
+    /// ```
+    public func dataStackEnvironment(_ stack: any DataStack) -> some View {
+        self
+            .environment(\.dataStack, stack)
+            .environment(\.managedObjectContext, stack.viewContext)
+    }
+}
+
+/// A property wrapper that accesses a `DataStack` from the view environment.
+///
+/// You must set the `DataStack` into the environment in a parent view to be able to access this environment
+/// variable this way. Otherwise, attempting to access `EnvironmentDataStack` will cause a fatal error.
+///
+/// ```swift
+/// struct ParentView: View {
+///     var dataStack: MyDataStack
+///
+///     var body: some View {
+///         ChildView()
+///             .dataStackEnvironment(dataStack)
+///     }
+/// }
+///
+/// struct ChildView: View {
+///     // accesses ParentView.dataStack as (any DataStack)
+///     @EnvironmentDataStack var dataStack
+///
+///     // accesses ParentView.dataStack.viewContext
+///     @Environment(\.managedObjectContext) var viewContext
+///
+///     var body: some View {
+///         Text("Hello World")
+///     }
+/// }
+/// ```
+@propertyWrapper public struct EnvironmentDataStack: DynamicProperty {
+    @Environment(\.dataStack) var env: (any DataStack)?
+    
+    public init() {
+        _env = Environment(\.dataStack)
+    }
+    
+    public var wrappedValue: any DataStack {
+        if let env {
+            return env
+        } else {
+            fatalError("Attempted to access environment DataStack, but none was found")
+        }
+    }
+}
+
+fileprivate extension EnvironmentValues {
+    var dataStack: (any DataStack)? {
+        get { self[DataStackKey.self] }
+        set { self[DataStackKey.self] = newValue }
+    }
+}
+
+fileprivate struct DataStackKey: EnvironmentKey {
+    static let defaultValue: (any DataStack)? = nil
+}