| /* |
| * Copyright 2014 Google Inc. All rights reserved. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef FRUIT_PROVIDER_H |
| #define FRUIT_PROVIDER_H |
| |
| // This include is not required here, but having it here shortens the include trace in error messages. |
| #include <fruit/impl/injection_errors.h> |
| |
| #include <fruit/component.h> |
| |
| namespace fruit { |
| |
| /** |
| * A Provider is a class that allows access to instances of the types used as parameters of the Provider template. |
| * It's possible to inject a Provider<MyClass> instead of MyClass itself, and this allows lazy injection. |
| * For example: |
| * |
| * class S { |
| * private: |
| * Bar* bar = nullptr; |
| * |
| * public: |
| * INJECT(S(Foo* foo, Provider<Bar> barProvider)) { |
| * if (foo->needsBar()) { |
| * bar = barProvider.get(); |
| * } |
| * } |
| * }; |
| * |
| * In the example above, Bar will only be created if get<Bar*> is called. |
| * This can be useful if Bar is expensive to create (or some other types that need to be injected when a Bar is injected are) |
| * or if there are other side effects of the Bar constructor that are undesirable when !foo->needsBar(). |
| * It's also possible to store the Provider object in a field, and create the Bar instance when the first method that needs it is |
| * called: |
| * |
| * class S { |
| * private: |
| * Provider<Bar> barProvider; |
| * |
| * public: |
| * INJECT(S(Provider<Bar> barProvider)) |
| * : barProvider(barProvider) { |
| * } |
| * |
| * void execute() { |
| * if (...) { |
| * Bar* bar = barProvider.get(); |
| * ... |
| * } |
| * } |
| * }; |
| * |
| * As usual, Fruit ensures that (at most) one instance is ever created in a given injector, so if the Bar object was already |
| * constructed, the get() will simply return it. |
| */ |
| template <typename C> |
| class Provider { |
| public: |
| |
| // Equivalent to get<C*>(). |
| C* get(); |
| |
| /** |
| * Returns an instance of the specified type. The following variations are allowed: |
| * |
| * get<C>() |
| * get<C*>() |
| * get<C&>() |
| * get<const C*>() |
| * get<const C&>() |
| * get<shared_ptr<C>>() |
| * |
| * The shared_ptr version comes with a slight performance hit, avoid it if possible. |
| * Calling get<> repeatedly for the same class with the same injector will return the same instance (except for the first |
| * variation above, that returns a value; in that case, another copy of the same instance will be returned). |
| */ |
| template <typename T> |
| T get(); |
| |
| /** |
| * This is a convenient way to call get(). E.g.: |
| * |
| * C& x(injector); |
| * |
| * is equivalent to: |
| * |
| * C& x = injector.get<C&>(); |
| */ |
| template <typename T> |
| explicit operator T(); |
| |
| private: |
| using Check1 = typename fruit::impl::meta::CheckIfError<fruit::impl::meta::Eval<fruit::impl::meta::CheckNormalizedTypes(fruit::impl::meta::Type<C>)>>::type; |
| // Force instantiation of Check1. |
| static_assert(true || sizeof(Check1), ""); |
| |
| using Check2 = typename fruit::impl::meta::CheckIfError<fruit::impl::meta::Eval<fruit::impl::meta::CheckNotAnnotatedTypes(fruit::impl::meta::Type<C>)>>::type; |
| // Force instantiation of Check2. |
| static_assert(true || sizeof(Check2), ""); |
| |
| // This is NOT owned by the provider object. It is not deleted on destruction. |
| // This is never nullptr. |
| fruit::impl::InjectorStorage* storage; |
| fruit::impl::InjectorStorage::Graph::node_iterator itr; |
| |
| Provider(fruit::impl::InjectorStorage* storage, fruit::impl::InjectorStorage::Graph::node_iterator itr); |
| |
| friend class fruit::impl::InjectorStorage; |
| |
| template <typename T> |
| friend struct fruit::impl::GetHelper; |
| |
| template <typename... OtherPs> |
| friend class Injector; |
| }; |
| |
| } // namespace fruit |
| |
| #include <fruit/impl/provider.defn.h> |
| |
| #endif // FRUIT_PROVIDER_H |