Avoid unnecessary use of std::function

5 files changed, 14 insertions, 7 deletions

diff --git a/platform/android/src/style/android_conversion.hpp b/platform/android/src/style/android_conversion.hpp
index 9b0ddbb50a..fbf5e2cd62 100644
--- a/platform/android/src/style/android_conversion.hpp
+++ b/platform/android/src/style/android_conversion.hpp
@@ -46,7 +46,8 @@ public:
         }
     }
 
-    static optional<Error> eachMember(const mbgl::android::Value&, const std::function<optional<Error> (const std::string&, const mbgl::android::Value&)>&) {
+    template <class Fn>
+    static optional<Error> eachMember(const mbgl::android::Value&, Fn&&) {
         // TODO
         mbgl::Log::Warning(mbgl::Event::Android, "eachMember not implemented");
         return {};
diff --git a/platform/darwin/src/MGLConversion.h b/platform/darwin/src/MGLConversion.h
index 1edb387a99..0d18d4e716 100644
--- a/platform/darwin/src/MGLConversion.h
+++ b/platform/darwin/src/MGLConversion.h
@@ -58,7 +58,12 @@ public:
         }
     }
 
-    static optional<Error> eachMember(const Holder& holder, const std::function<optional<Error> (const std::string&, const Holder&)>& fn) {
+// Compiler is wrong about `Fn` parameter missing a nullability specifier.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+    template <class Fn>
+    static optional<Error> eachMember(const Holder&, Fn&&) {
+#pragma clang diagnostic pop
         // Not implemented (unneeded for MGLStyleFunction conversion).
         NSCAssert(NO, @"eachMember not implemented");
         return {};
diff --git a/platform/node/src/node_conversion.hpp b/platform/node/src/node_conversion.hpp
index 04494eb142..ed457c1a39 100644
--- a/platform/node/src/node_conversion.hpp
+++ b/platform/node/src/node_conversion.hpp
@@ -59,7 +59,8 @@ public:
         return {scope.Escape(result.ToLocalChecked())};
     }
 
-    static optional<Error> eachMember(const v8::Local<v8::Value>& value, const std::function<optional<Error> (const std::string&, const v8::Local<v8::Value>&)>& fn) {
+    template <class Fn>
+    static optional<Error> eachMember(const v8::Local<v8::Value>& value, Fn&& fn) {
         Nan::HandleScope scope;
         v8::Local<v8::Array> names = Nan::GetOwnPropertyNames(Nan::To<v8::Object>(value).ToLocalChecked()).ToLocalChecked();
         for (uint32_t i = 0; i < names->Length(); ++i) {
diff --git a/platform/qt/src/qt_conversion.hpp b/platform/qt/src/qt_conversion.hpp
index 91d5d48c12..eaeb391db0 100644
--- a/platform/qt/src/qt_conversion.hpp
+++ b/platform/qt/src/qt_conversion.hpp
@@ -53,9 +53,8 @@ public:
         }
     }
 
-    using EachMemberFn = std::function<optional<Error>(const std::string&, const QVariant&)>;
-
-    static optional<Error> eachMember(const QVariant& value, const EachMemberFn& fn) {
+    template <class Fn>
+    static optional<Error> eachMember(const QVariant& value, Fn&& fn) {
         auto map = value.toMap();
         auto iter = map.constBegin();
 
diff --git a/src/mbgl/style/rapidjson_conversion.hpp b/src/mbgl/style/rapidjson_conversion.hpp
index 967f1d829c..79bd9c928b 100644
--- a/src/mbgl/style/rapidjson_conversion.hpp
+++ b/src/mbgl/style/rapidjson_conversion.hpp
@@ -41,7 +41,8 @@ public:
         return {member};
     }
 
-    static optional<Error> eachMember(const JSValue* value, const std::function<optional<Error> (const std::string&, const JSValue* const&)>& fn) {
+    template <class Fn>
+    static optional<Error> eachMember(const JSValue* value, Fn&& fn) {
         assert(value->IsObject());
         for (const auto& property : value->GetObject()) {
             optional<Error> result =