fix: generic loading of host functions in C++ (#315)

## Description

Add generic loading of host functions in C++.

### Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Documentation update (improves or adds clarity to existing
documentation)

### Tested on

- [x] iOS
- [x] Android

Author: JakubGonera

common/rnexecutorch/RnExecutorchInstaller.cpp

@@ -1,8 +1,7 @@
 #include "RnExecutorchInstaller.h"
 
 #include <rnexecutorch/host_objects/JsiConversions.h>
-#include <rnexecutorch/host_objects/ModelHostObject.h>
-#include <rnexecutorch/models/StyleTransfer.h>
+#include <rnexecutorch/models/style_transfer/StyleTransfer.h>
 
 namespace rnexecutorch {
 
@@ -11,50 +10,14 @@ namespace rnexecutorch {
 // SSL intricacies manually, as it is done automagically in ObjC++/Kotlin.
 FetchUrlFunc_t fetchUrlFunc;
 
-jsi::Function RnExecutorchInstaller::loadStyleTransfer(
-    jsi::Runtime *jsiRuntime,
-    const std::shared_ptr<react::CallInvoker> &jsCallInvoker) {
-  return jsi::Function::createFromHostFunction(
-      *jsiRuntime, jsi::PropNameID::forAscii(*jsiRuntime, "loadStyleTransfer"),
-      0,
-      [jsCallInvoker](jsi::Runtime &runtime, const jsi::Value &thisValue,
-                      const jsi::Value *args, size_t count) -> jsi::Value {
-        assert(count == 1);
-        try {
-          auto source = jsiconversion::getValue<std::string>(args[0], runtime);
-
-          auto styleTransferPtr =
-              std::make_shared<StyleTransfer>(source, &runtime);
-          auto styleTransferHostObject =
-              std::make_shared<ModelHostObject<StyleTransfer>>(styleTransferPtr,
-                                                               jsCallInvoker);
-
-          return jsi::Object::createFromHostObject(runtime,
-                                                   styleTransferHostObject);
-        } catch (const std::runtime_error &e) {
-          // This catch should be merged with the next one
-          // (std::runtime_error inherits from std::exception) HOWEVER react
-          // native has broken RTTI which breaks proper exception type
-          // checking. Remove when the following change is present in our
-          // version:
-          // https://github.com/facebook/react-native/commit/3132cc88dd46f95898a756456bebeeb6c248f20e
-          throw jsi::JSError(runtime, e.what());
-        } catch (const std::exception &e) {
-          throw jsi::JSError(runtime, e.what());
-        } catch (...) {
-          throw jsi::JSError(runtime, "Unknown error");
-        }
-      });
-}
-
 void RnExecutorchInstaller::injectJSIBindings(
-    jsi::Runtime *jsiRuntime,
-    const std::shared_ptr<react::CallInvoker> &jsCallInvoker,
+    jsi::Runtime *jsiRuntime, std::shared_ptr<react::CallInvoker> jsCallInvoker,
     FetchUrlFunc_t fetchDataFromUrl) {
   fetchUrlFunc = fetchDataFromUrl;
 
   jsiRuntime->global().setProperty(
       *jsiRuntime, "loadStyleTransfer",
-      loadStyleTransfer(jsiRuntime, jsCallInvoker));
+      RnExecutorchInstaller::loadModel<StyleTransfer>(jsiRuntime, jsCallInvoker,
+                                                      "loadStyleTransfer"));
 }
 } // namespace rnexecutorch

common/rnexecutorch/RnExecutorchInstaller.h

@@ -7,23 +7,71 @@
 #include <ReactCommon/CallInvoker.h>
 #include <jsi/jsi.h>
 
+#include <rnexecutorch/host_objects/JsiConversions.h>
+#include <rnexecutorch/host_objects/ModelHostObject.h>
+
 namespace rnexecutorch {
 
 using FetchUrlFunc_t = std::function<std::vector<std::byte>(std::string)>;
+extern FetchUrlFunc_t fetchUrlFunc;
 
 using namespace facebook;
 
 class RnExecutorchInstaller {
 public:
   static void
   injectJSIBindings(jsi::Runtime *jsiRuntime,
-                    const std::shared_ptr<react::CallInvoker> &jsCallInvoker,
+                    std::shared_ptr<react::CallInvoker> jsCallInvoker,
                     FetchUrlFunc_t fetchDataFromUrl);
 
 private:
+  template <typename ModelT>
   static jsi::Function
-  loadStyleTransfer(jsi::Runtime *jsiRuntime,
-                    const std::shared_ptr<react::CallInvoker> &jsCallInvoker);
+  loadModel(jsi::Runtime *jsiRuntime,
+            std::shared_ptr<react::CallInvoker> jsCallInvoker,
+            const std::string &loadFunctionName) {
+
+    return jsi::Function::createFromHostFunction(
+        *jsiRuntime, jsi::PropNameID::forAscii(*jsiRuntime, loadFunctionName),
+        0,
+        [jsCallInvoker](jsi::Runtime &runtime, const jsi::Value &thisValue,
+                        const jsi::Value *args, size_t count) -> jsi::Value {
+          if (count != 1) {
+            char errorMessage[100];
+            std::snprintf(
+                errorMessage, sizeof(errorMessage),
+                "Argument count mismatch, was expecting: 1 but got: %zu",
+                count);
+            throw jsi::JSError(runtime, errorMessage);
+          }
+          try {
+            auto source =
+                jsiconversion::getValue<std::string>(args[0], runtime);
+
+            auto modelImplementationPtr =
+                std::make_shared<ModelT>(source, &runtime);
+            auto modelHostObject = std::make_shared<ModelHostObject<ModelT>>(
+                modelImplementationPtr, jsCallInvoker);
+
+            return jsi::Object::createFromHostObject(runtime, modelHostObject);
+          } catch (const std::runtime_error &e) {
+            // This catch should be merged with the next one
+            // (std::runtime_error inherits from std::exception) HOWEVER react
+            // native has broken RTTI which breaks proper exception type
+            // checking. Remove when the following change is present in our
+            // version:
+            // https://github.com/facebook/react-native/commit/3132cc88dd46f95898a756456bebeeb6c248f20e
+            throw jsi::JSError(runtime, e.what());
+            return jsi::Value();
+          } catch (const std::exception &e) {
+            throw jsi::JSError(runtime, e.what());
+            return jsi::Value();
+          } catch (...) {
+            throw jsi::JSError(runtime, "Unknown error");
+            return jsi::Value();
+          }
+        });
+  }
 };
 
 } // namespace rnexecutorch

common/rnexecutorch/host_objects/JsiConversions.h

@@ -12,22 +12,23 @@ using namespace facebook;
 template <typename T> T getValue(const jsi::Value &val, jsi::Runtime &runtime);
 
 template <>
-double getValue<double>(const jsi::Value &val, jsi::Runtime &runtime) {
+inline double getValue<double>(const jsi::Value &val, jsi::Runtime &runtime) {
   return val.asNumber();
 }
 
-template <> bool getValue<bool>(const jsi::Value &val, jsi::Runtime &runtime) {
+template <>
+inline bool getValue<bool>(const jsi::Value &val, jsi::Runtime &runtime) {
   return val.asBool();
 }
 
 template <>
-std::string getValue<std::string>(const jsi::Value &val,
-                                  jsi::Runtime &runtime) {
+inline std::string getValue<std::string>(const jsi::Value &val,
+                                         jsi::Runtime &runtime) {
   return val.getString(runtime).utf8(runtime);
 }
 
 template <>
-std::vector<std::string>
+inline std::vector<std::string>
 getValue<std::vector<std::string>>(const jsi::Value &val,
                                    jsi::Runtime &runtime) {
   jsi::Array array = val.asObject(runtime).asArray(runtime);
@@ -49,15 +50,15 @@ getValue<std::vector<std::string>>(const jsi::Value &val,
 // we add a function here.
 
 // Identity function for the sake of completeness
-jsi::Value getJsiValue(jsi::Value &&value, jsi::Runtime &runtime) {
+inline jsi::Value getJsiValue(jsi::Value &&value, jsi::Runtime &runtime) {
   return std::move(value);
 }
 
-jsi::Value getJsiValue(jsi::Object &&value, jsi::Runtime &runtime) {
+inline jsi::Value getJsiValue(jsi::Object &&value, jsi::Runtime &runtime) {
   return jsi::Value(std::move(value));
 }
 
-jsi::Value getJsiValue(const std::string &str, jsi::Runtime &runtime) {
+inline jsi::Value getJsiValue(const std::string &str, jsi::Runtime &runtime) {
   return jsi::String::createFromAscii(runtime, str);
 }