Add access control for components

.gitignore

@@ -29,6 +29,7 @@
 .fseventsd
 .LSOverride
 .Spotlight-V100
+.swiftpm/
 .TemporaryItems
 .Trashes
 .VolumeIcon.icns
@@ -51,4 +52,4 @@ playground.xcworkspace
 Temporary Items
 timeline.xctimeline
 xcuserdata
-xcuserdata/Package.resolveddocs/
+xcuserdata/Package.resolveddocs/

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.0.0
+// swift-tools-version:5.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription

Sources/FirebladeECS/Component+Access.swift

@@ -0,0 +1,33 @@
+//
+//  Component+Access.swift
+//  
+//
+//  Created by Christian Treffs on 25.06.19.
+//
+
+@dynamicMemberLookup
+public struct ReadableOnly<Comp> where Comp: Component {
+    @usableFromInline let component: Comp
+    
+    public init(_ component: Comp) {
+        self.component = component
+    }
+    
+    @inlinable public subscript<C>(dynamicMember keyPath: KeyPath<Comp, C>) -> C {
+        return component[keyPath: keyPath]
+    }
+}
+
+@dynamicMemberLookup
+public struct Writable<Comp> where Comp: Component {
+    @usableFromInline let component: Comp
+    
+    public init(_ component: Comp) {
+        self.component = component
+    }
+    
+    @inlinable public subscript<C>(dynamicMember keyPath: ReferenceWritableKeyPath<Comp, C>) -> C {
+        nonmutating get { return component[keyPath: keyPath] }
+        nonmutating set { component[keyPath: keyPath] = newValue }
+    }
+}

Tests/FirebladeECSTests/AccessTests.swift

@@ -0,0 +1,43 @@
+//
+//  AccessTests.swift
+//  
+//
+//  Created by Christian Treffs on 25.06.19.
+//
+
+
+
+import FirebladeECS
+import XCTest
+
+class AccessTests: XCTestCase {
+
+    func testReadOnly() {
+        let pos = Position(x: 1, y: 2)
+        
+        let readable = ReadableOnly<Position>(pos)
+        
+        XCTAssertEqual(readable.x, 1)
+        XCTAssertEqual(readable.y, 2)
+        
+        // readable.x = 3 // does not work and that's correct!
+    }
+    
+    func testWrite() {
+        let pos = Position(x: 1, y: 2)
+        
+        let writable = Writable<Position>(pos)
+        
+        XCTAssertEqual(writable.x, 1)
+        XCTAssertEqual(writable.y, 2)
+        
+        writable.x = 3
+        
+        XCTAssertEqual(writable.x, 3)
+        XCTAssertEqual(pos.x, 3)
+
+        XCTAssertEqual(writable.y, 2)
+        XCTAssertEqual(pos.y, 2)
+
+    }
+}