feat: fetch eraser objects instead of loading from stroke

Memola/Canvas/Contexts/GraphicContext.swift

@@ -160,7 +160,7 @@ extension GraphicContext {
                 thickness: pen.thickness
             )
             eraserStroke.graphicContext = self
-            withPersistence(\.backgroundContext) { [_stroke = eraserStroke] context in
+            withPersistence(\.backgroundContext) { [graphicContext = object, _stroke = eraserStroke] context in
                 let stroke = EraserObject(\.backgroundContext)
                 stroke.bounds = _stroke.bounds
                 stroke.color = _stroke.color
@@ -169,6 +169,8 @@ extension GraphicContext {
                 stroke.createdAt = _stroke.createdAt
                 stroke.quads = []
                 stroke.strokes = .init()
+                stroke.graphicContext = graphicContext
+                graphicContext?.erasers.add(stroke)
                 _stroke.object = stroke
                 try context.saveIfNeeded()
             }

Memola/Canvas/Geometries/Stroke/Strokes/PenStroke.swift

@@ -81,8 +81,8 @@ final class PenStroke: Stroke, @unchecked Sendable {
             guard let quad = quad as? QuadObject else { return nil }
             return Quad(object: quad)
         }
-        eraserStrokes = Set(object.erasers.compactMap { [graphicContext] eraser -> EraserStroke? in
+        let erasers = fetchErasers(of: object)
-            guard let eraser = eraser as? EraserObject else { return nil }
+        eraserStrokes = Set(erasers.compactMap { [graphicContext] eraser -> EraserStroke? in
             let url = eraser.objectID.uriRepresentation()
             return graphicContext.barrierQueue.sync(flags: .barrier) {
                 if graphicContext.erasers[url] == nil {
@@ -96,6 +96,19 @@ final class PenStroke: Stroke, @unchecked Sendable {
         })
     }
 
+    func fetchErasers(of stroke: StrokeObject) -> [EraserObject] {
+        let fetchRequest: NSFetchRequest<EraserObject> = .init(entityName: "EraserObject")
+        fetchRequest.predicate = NSPredicate(format: "ANY strokes == %@", stroke)
+
+        do {
+            let erasers = try Persistence.shared.backgroundContext.fetch(fetchRequest)
+            return erasers
+        } catch {
+            NSLog("[Memola] - \(error.localizedDescription)")
+        }
+        return []
+    }
+
     func addQuad(at point: CGPoint, rotation: CGFloat, shape: QuadShape) {
         let quad = Quad(
             origin: point,

Memola/Features/Memos/MemosView.swift

@@ -85,6 +85,7 @@ struct MemosView: View {
 
         let graphicContextObject = GraphicContextObject(\.viewContext)
         graphicContextObject.strokes = []
+        graphicContextObject.erasers = .init()
 
         memoObject.canvas = canvasObject
         memoObject.tool = toolObject

Memola/Persistence/Objects/EraserObject.swift

@@ -17,4 +17,5 @@ final class EraserObject: NSManagedObject {
     @NSManaged var thickness: CGFloat
     @NSManaged var quads: NSMutableOrderedSet
     @NSManaged var strokes: NSMutableSet
+    @NSManaged var graphicContext: GraphicContextObject?
 }

Memola/Persistence/Objects/GraphicContextObject.swift

@@ -12,4 +12,5 @@ import Foundation
 final class GraphicContextObject: NSManagedObject {
     @NSManaged var canvas: CanvasObject?
     @NSManaged var strokes: NSMutableOrderedSet
+    @NSManaged var erasers: NSMutableSet
 }

Memola/Resources/Models/MemolaModel.xcdatamodeld/MemolaModel.xcdatamodel/contents

@@ -12,11 +12,13 @@
         <attribute name="createdAt" attributeType="Date" usesScalarValueType="NO"/>
         <attribute name="style" attributeType="Integer 16" defaultValueString="0" usesScalarValueType="YES"/>
         <attribute name="thickness" attributeType="Double" defaultValueString="0.0" usesScalarValueType="YES"/>
+        <relationship name="graphicContext" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="GraphicContextObject" inverseName="erasers" inverseEntity="GraphicContextObject"/>
         <relationship name="quads" toMany="YES" deletionRule="Cascade" ordered="YES" destinationEntity="QuadObject" inverseName="eraser" inverseEntity="QuadObject"/>
         <relationship name="strokes" toMany="YES" deletionRule="Nullify" destinationEntity="StrokeObject" inverseName="erasers" inverseEntity="StrokeObject"/>
     </entity>
     <entity name="GraphicContextObject" representedClassName="GraphicContextObject" syncable="YES">
         <relationship name="canvas" optional="YES" maxCount="1" deletionRule="Nullify" destinationEntity="CanvasObject" inverseName="graphicContext" inverseEntity="CanvasObject"/>
+        <relationship name="erasers" toMany="YES" deletionRule="Cascade" destinationEntity="EraserObject" inverseName="graphicContext" inverseEntity="EraserObject"/>
         <relationship name="strokes" toMany="YES" deletionRule="Cascade" ordered="YES" destinationEntity="StrokeObject" inverseName="graphicContext" inverseEntity="StrokeObject"/>
     </entity>
     <entity name="MemoObject" representedClassName="MemoObject" syncable="YES">