cppdi

cppdi is a header-only c++17 library that brings dependency injection to C++. It’s heavily inspired by DI provided by ASP.NET.

Installation

Simply drop the header file in your project or add the include directory to your include paths.

Usage

Here’s a simple example of using the dependency injection container.

#include <iostream>
#include "Container.hpp"
class IGreeter
{
public:
    virtual void Greet() = 0;
}
class HelloWorldGreeter : public IGreeter
{
public:
    void Greet() override
    {
        std::cout << "Hello, world!\n";
    }
}
int main()
{
    cppdi::Container container;
    container.AddSingleton<IGreeter, HelloWorldGreeter>();
    auto greeter = container.GetRequiredService<IGreeter>();
    greeter->Greet();
    return 0;
}

This outputs Hello, world!

Non-parameterless constructors

If your class doesn’t have a parameterless constructor (which is usually the case) you’ll have to create a template specialization for your types in cppdi namespace. An example specialization will look like this:

namespace cppdi
{
    template <>
    std::shared_ptr<ISerializer> CreateInstance<ISerializer, JsonSerializer>(const Container &container)
    {
        auto configuration = container.GetRequiredService<IConfiguration>();
        auto instance = std::make_shared<JsonSerializer>(configuration); // Let's assume that JsonSerializer takes a shared_ptr<IConfiguration> as a parameter
        return instance;
    }
}

There are more ways you can register implementations of interfaces and they are documented in the Container.hpp file.