A C++ Dependency Injection framework

This repository contains:

• Source code: src and inc folders
• Small example: example folder

After build the project (see: Building the library and running the example) there will be two more folders:

• compiled library : lib folder
• compiled example : bin folder

Limitations:

• It can only instantiate transient objects
• Registered services cannot have more than 1 dependency
• Registered services cannot have any input parameter in the constructor

Usage:

1. Service interface classes must derive from ServiceBase.

2. To register services:

   If the service has no dependencies:

    IocContainer::GetSingleton().RegisterService<ServiceInterface, ServiceImplementation>();
   

   If it has one dependency:

    IocContainer::GetSingleton().RegisterService<ServiceInterface, ServiceImplementation, ServiceDependency>();
   

3. Instantiate objects:

    IocContainer::GetSingleton().GetService<ServiceInterface>();
   

4. To remove services:

    IocContainer::GetSingleton().RemoveService<ServiceInterface>();
   

Example: VideoPlayer

In this example, an hypothetical VideoPlayer uses 2 services to accomplish the task of presenting frames in the screen: a Decoder to decode frames, and a Logger to record all ongoing actions. VideoPlayer depends on the Decoder, and the Decoder depends on the Logger.

The chain of dependencies is: VideoPlayer->Decoder->Logger

In the first part of main function:

• These 3 services are registered in the IocContainer.
• VideoPlayer and it's dependencies are instantiated and VideoPlayer::PresentFrame() is successfully called.

In the second part, cyclic dependency case is presented:

• A similar environment than before, but a new Logger implementation has a dependency on the VideoPlayer, making the circular dependency VideoPlayer->Decoder->Logger->VideoPlayer
• An exception is raised when trying to instantiate the VideoPlayer object

(this example don't include any real implementation apart of the Dependency Injection Container)

Building the library and running the example

Clone the repo

git clone -b ioc_container https://github.com/SCVready/cpp_service_locator ioc_container;
cd ioc_container;

Build/running locally (Linux/Ubuntu20.04):

Install dependencies:

sudo apt install -y build-essential libgtest-dev libgmock-dev cmake;

Run and build:

./build.sh;

Build/running in Docker (Linux):

docker run -it -v $(pwd):/service_locator --workdir /service_locator --user 1000:1000 scvready/ubuntu-gtest:latest ./build.sh;