updated api for fetch instead of get

engine/core/src/ecs.zig

@@ -306,7 +306,19 @@ pub const Entity = struct {
         return rv;
     }
 
+    pub fn fetch(self: @This(), comptime Component: type) ?*Component {
+        if (@TypeOf(Component.BaseContainer.*).StableReferences) {
+            @compileError(@typeName(Component) ++ " states that it's references are stable, use get() instead of fetch()");
+        }
+        const rv = Component.BaseContainer.get(self.handle);
+        return if (rv == null) null else @ptrCast(@alignCast(rv.?));
+    }
+
+    // acquire a reference to an entity's component if it exists
     pub fn get(self: @This(), comptime Component: type) ?*Component {
+        if (!@TypeOf(Component.BaseContainer.*).StableReferences) {
+            @compileError(@typeName(Component) ++ " doesn't state that it's references are stable, use fetch() instead of get()");
+        }
         const rv = Component.BaseContainer.get(self.handle);
         return if (rv == null) null else @ptrCast(@alignCast(rv.?));
     }

engine/physics/src/physicsCharacter.zig

@@ -12,7 +12,7 @@ pub const PhysicsCharacter = struct {
             @panic("adding a physics character to an entity already controlled by PhysicsCollider. I'm not going to support this");
         }
 
-        if (self.entity.get(core.Scene) == null) {
+        if (self.entity.fetch(core.Scene) == null) {
             @panic("a scene component needs to be created in order to add a physics collider");
         }
     }
@@ -23,7 +23,7 @@ pub const PhysicsCharacter = struct {
         const interface = system.system.getBodyInterfaceMut();
         const shape = system.shapes.get(n.handle()).?;
 
-        const scene = self.entity.get(core.Scene).?;
+        const scene = self.entity.fetch(core.Scene).?;
         const p = scene.getPosition();
 
         var settings = try zphysics.CharacterSettings.create();
@@ -51,7 +51,7 @@ pub const PhysicsCharacter = struct {
         _ = dt;
         // self.character.update(@floatCast(dt), .{ 0, -1.0, 0 }, .{});
 
-        const scene = self.entity.get(core.Scene).?;
+        const scene = self.entity.fetch(core.Scene).?;
         const p = self.character.getPosition();
         // core.debugSphere(position, 20, .{});
         scene.setPosition(.{ .x = p[0], .y = p[1], .z = p[2] });

engine/physics/src/physicsCollider.zig

@@ -12,7 +12,7 @@ pub const PhysicsCollider = struct {
             @panic("adding a physics collider to an entity already controlled by physics character. I don't want to support this");
         }
 
-        if (self.entity.get(core.Scene) == null) {
+        if (self.entity.fetch(core.Scene) == null) {
             @panic("a scene component needs to be created in order to add a physics collider");
         }
     }

engine/physics/src/physicsSystem.zig

@@ -212,7 +212,7 @@ pub const PhysicsRuntime = struct {
                 defer readLock.unlock();
 
                 if (readLock.body) |body| {
-                    const scene = collider.entity.get(core.Scene).?;
+                    const scene = collider.entity.fetch(core.Scene).?;
                     scene.setPosition(core.Vectorf.fromArray(body.position));
                     scene.setRotation(.{ .quat = body.rotation });
                 }

engine/rend/src/camera/CameraComponent.zig

@@ -41,7 +41,7 @@ pub fn updateProjections(self: *@This()) void {
 }
 
 pub fn resolve(self: *@This()) void {
-    const scene = self.entity.get(core.Scene).?;
+    const scene = self.entity.fetch(core.Scene).?;
 
     self.updateProjections();
 

engine/rend/src/meshes/MeshComponent.zig

@@ -21,7 +21,7 @@ pub fn initECS(self: *@This(), handle: core.SetHandle) void {
     // get the mesh component
     self.entity = core.Entity{ .handle = handle };
 
-    if (self.entity.get(core.Scene) == null) {
+    if (self.entity.fetch(core.Scene) == null) {
         @panic("mesh added to something that doesn't have a scene component, not supported");
     }
 }

lib/p2/src/structures/sparse-set.zig

@@ -55,6 +55,8 @@ pub fn SparseMultiSetAdvanced(comptime T: type, comptime SparseSize: u32) type {
 
         pub const IsMultiset = true;
 
+        pub const StableReferences = false;
+
         pub fn init(allocator: std.mem.Allocator) @This() {
             var self = @This(){
                 .allocator = allocator,
@@ -308,6 +310,8 @@ pub fn SparseSetAdvanced(comptime T: type, comptime SparseSize: u32) type {
         containerListener: ?ContainerListener = null,
         opCount: u32 = 0,
 
+        pub const StableReferences = false;
+
         pub fn getStateCount(self: @This()) u32 {
             return self.opCount;
         }
@@ -587,6 +591,8 @@ pub fn SparseMap(comptime T: type) type {
         containerListener: ?ContainerListener = null,
         opCount: u32 = 0,
 
+        pub const StableReferences = true;
+
         pub fn create(backingAllocator: std.mem.Allocator) !*@This() {
             const self = try backingAllocator.create(@This());
 

projects/sampleGame/main.zig

@@ -134,7 +134,7 @@ pub fn onExit(ctx: ?*anyopaque, action: core.ActionEvent) void {
 
 pub fn tick(self: *@This(), dt: f64) void {
     const fdt: f32 = @floatCast(dt);
-    if (self.camera.get(core.Scene)) |scene| {
+    if (self.camera.fetch(core.Scene)) |scene| {
         const vector = core.Vectorf{ .x = self.moveVector.x, .z = self.moveVector.z, .y = self.verticalMove };
         scene.getPosRot().position = scene.getPosRot().position.add(vector.fmul(self.cameraSpeed * fdt));
         // core.engine_log(" camera position >> {any}", .{scene.getPosRot().position});