feat: add get() to Effect callback parameters

Author: marklawlor

cpp/Effect.hpp

@@ -9,12 +9,37 @@
 
 namespace reactnativecss {
 
+    // Forward declarations to allow Effect::GetProxy operators without including headers here
+    template<class T>
+    class Observable;
+
+    template<class T>
+    class Computed;
+
     class Effect {
     public:
-        using Callback = std::function<void()>;
+        struct GetProxy {
+            Effect *self;
+
+            template<class U>
+            inline const U &operator()(Observable<U> &obs) const noexcept {
+                return obs.get(*self);
+            }
+
+            template<class U>
+            inline const U &operator()(Computed<U> &comp) const noexcept {
+                return comp.get(*self);
+            }
+        };
+
+        using Callback = std::function<void(GetProxy &)>;
 
         explicit Effect(Callback cb) : callback_(std::move(cb)) {}
 
+        // Backward-compat: allow constructing with a no-arg callback
+        explicit Effect(std::function<void()> cb)
+                : callback_([fn = std::move(cb)](GetProxy &) { if (fn) fn(); }) {}
+
         Effect(const Effect &) = delete;
 
         Effect &operator=(const Effect &) = delete;
@@ -86,8 +111,10 @@ namespace reactnativecss {
         // Immediate execution helper
         void runImmediate() {
             dispose();
-            if (callback_)
-                callback_();
+            if (callback_) {
+                GetProxy g{this};
+                callback_(g);
+            }
         }
 
         // Per-thread batching state
@@ -107,4 +134,4 @@ namespace reactnativecss {
         }
     };
 
-} // namespace nitro
+} // namespace reactnativecss

cpp/ShadowTreeUpdateManager.cpp

@@ -16,6 +16,7 @@
 #include <cassert>
 
 namespace margelo::nitro::cssnitro {
+
     using jsi::Runtime;
     using reactnativecss::Observable;
     namespace nitro_ns = ::margelo::nitro;
@@ -151,17 +152,13 @@ namespace margelo::nitro::cssnitro {
         }
         if (runtime_effects_.find(rt) == runtime_effects_.end()) {
             auto obs = rtObsIt->second;
-            auto weakBox = std::make_shared<std::weak_ptr<reactnativecss::Effect>>();
             auto effect = std::make_shared<reactnativecss::Effect>(
-                    [obs, rt, weakBox]() {
-                        auto eff = weakBox->lock();
-                        if (!eff) return;
-                        const ShadowTreeUpdateManager::UpdatesMap &updates = obs->get(*eff);
+                    [obs, rt](reactnativecss::Effect::GetProxy &get) {
+                        const ShadowTreeUpdateManager::UpdatesMap &updates = get(*obs);
                         if (updates.empty()) return;
                         ShadowTreeUpdateManager::applyUpdates(*rt, updates);
                         obs->set(ShadowTreeUpdateManager::UpdatesMap{});
                     });
-            *weakBox = effect;
             effect->run();
             runtime_effects_.emplace(rt, std::move(effect));
         }