Prototyping SwiftUI utilities

Sources/LiveList.swift

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+//
+//  LiveList.swift
+//  CoreStore
+//
+//  Copyright © 2021 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+#if canImport(Combine) && canImport(SwiftUI)
+
+import Combine
+import SwiftUI
+
+
+// MARK: - LiveList
+
+@propertyWrapper
+@available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
+public struct LiveList<Object: DynamicObject>: DynamicProperty {
+    
+    // MARK: Public
+    
+    public typealias Items = ListSnapshot<Object>
+    
+    public init(
+        _ listPublisher: ListPublisher<Object>
+    ) {
+        
+        self.observer = .init(listPublisher: listPublisher)
+    }
+    
+    public init(
+        _ from: From<Object>,
+        _ fetchClauses: FetchClause...,
+        in dataStack: DataStack
+    ) {
+        
+        self.init(from, fetchClauses, in: dataStack)
+    }
+    
+    public init(
+        _ from: From<Object>,
+        _ fetchClauses: [FetchClause],
+        in dataStack: DataStack
+    ) {
+        
+        self.init(dataStack.publishList(from, fetchClauses))
+    }
+    
+    public init<B: FetchChainableBuilderType>(
+        _ clauseChain: B,
+        in dataStack: DataStack
+    ) where B.ObjectType == Object {
+        
+        self.init(dataStack.publishList(clauseChain))
+    }
+    
+    public init(
+        _ from: From<Object>,
+        _ sectionBy: SectionBy<Object>,
+        _ fetchClauses: FetchClause...,
+        in dataStack: DataStack
+    ) {
+        
+        self.init(from, sectionBy, fetchClauses, in: dataStack)
+    }
+    
+    public init(
+        _ from: From<Object>,
+        _ sectionBy: SectionBy<Object>,
+        _ fetchClauses: [FetchClause],
+        in dataStack: DataStack
+    ) {
+        
+        self.init(dataStack.publishList(from, sectionBy, fetchClauses))
+    }
+    
+    public init<B: SectionMonitorBuilderType>(
+        _ clauseChain: B,
+        in dataStack: DataStack
+    ) where B.ObjectType == Object {
+        
+        self.init(dataStack.publishList(clauseChain))
+    }
+    
+    
+    // MARK: @propertyWrapper
+    
+    public var wrappedValue: Items {
+        
+        return self.observer.items
+    }
+    
+    public var projectedValue: ListPublisher<Object> {
+        
+        return self.observer.listPublisher
+    }
+    
+    
+    // MARK: DynamicProperty
+    
+    public mutating func update() {
+        
+        self._observer.update()
+    }
+    
+    
+    // MARK: Private
+    
+    @ObservedObject
+    private var observer: Observer
+    
+    
+    // MARK: - Observer
+    
+    private final class Observer: ObservableObject {
+        
+        @Published
+        var items: Items
+        
+        let listPublisher: ListPublisher<Object>
+        
+        init(listPublisher: ListPublisher<Object>) {
+            
+            self.listPublisher = listPublisher
+            self.items = listPublisher.snapshot
+            
+            listPublisher.addObserver(self) { [weak self] (listPublisher) in
+                
+                guard let self = self else {
+                    
+                    return
+                }
+                self.items = listPublisher.snapshot
+            }
+        }
+        
+        deinit {
+            
+            self.listPublisher.removeObserver(self)
+        }
+    }
+}
+
+#endif