Prototyping SwiftUI utilities

Sources/ObjectReader.swift

@@ -1,9 +1,26 @@
 //
-//  ListState.swift
+//  ObjectReader.swift
 //  CoreStore
 //
-//  Created by John Rommel Estropia on 2020/12/26.
-//  Copyright © 2020 John Rommel Estropia. All rights reserved.
+//  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)
@@ -15,40 +32,29 @@ import SwiftUI
 // MARK: - ObjectReader
 
 @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
-public struct ObjectReader<Object: DynamicObject, Content: View, Placeholder: View>: View {
+public struct ObjectReader<Object: DynamicObject, Content: View, Value>: View {
     
     // MARK: Internal
     
     public init(
         _ objectPublisher: ObjectPublisher<Object>?,
-        @ViewBuilder content: @escaping (ObjectSnapshot<Object>) -> Content,
-        @ViewBuilder placeholder: @escaping () -> Placeholder
-    ) {
+        @ViewBuilder content: @escaping (Value) -> Content
+    ) where Value == LiveObject<Object>.Item {
         
-        self.objectPublisher = .init(
-            objectPublisher.flatMap {
-                
-                guard let dataStack = $0.cs_dataStack() else {
-                    
-                    return nil
-                }
-                return $0.asPublisher(in: dataStack)
-            }
-        )
+        self._object = .init(objectPublisher)
         self.content = content
-        self.placeholder = placeholder
+        self.keyPath = \.self
     }
     
     public init(
         _ objectPublisher: ObjectPublisher<Object>?,
-        @ViewBuilder content: @escaping (ObjectSnapshot<Object>) -> Content
-    ) where Placeholder == EmptyView {
+        keyPath: KeyPath<LiveObject<Object>.Item, Value>,
+        @ViewBuilder content: @escaping (Value) -> Content
+    ) {
         
-        self.init(
-            objectPublisher,
-            content: content,
-            placeholder: EmptyView.init
-        )
+        self._object = .init(objectPublisher)
+        self.content = content
+        self.keyPath = keyPath
     }
     
     
@@ -56,45 +62,20 @@ public struct ObjectReader<Object: DynamicObject, Content: View, Placeholder: Vi
     
     public var body: some View {
         
-        if let snapshot = self.objectPublisher.wrappedValue?.snapshot {
+        if let object = self.object {
             
-            self.content(snapshot)
-        }
-        else {
-            
-            self.placeholder()
+            self.content(object[keyPath: self.keyPath])
         }
     }
     
     
     // MARK: Private
     
-    @ObservedObject
-    private var objectPublisher: OptionalObservedObject<ObjectPublisher<Object>>
+    @LiveObject
+    private var object: LiveObject<Object>.Item?
     
-    private let content: (ObjectSnapshot<Object>) -> Content
-    private let placeholder: () -> Placeholder
-    
-    
-    // MARK: - OptionalObservedObject
-    
-    fileprivate final class OptionalObservedObject<T: ObservableObject>: ObservableObject where ObservableObjectPublisher == T.ObjectWillChangePublisher {
-        
-        // MARK: Internal
-        
-        let wrappedValue: T?
-        
-        init(_ wrappedValue: T?) {
-            
-            self.wrappedValue = wrappedValue
-            self.objectWillChange = wrappedValue.map(\.objectWillChange) ?? .init()
-        }
-        
-        // MARK: ObservableObject
-        
-        let objectWillChange: ObservableObjectPublisher
-    }
+    private let content: (Value) -> Content
+    private let keyPath: KeyPath<LiveObject<Object>.Item, Value>
 }
 
 #endif
-