C++20/C++23 Dependency Injection

Dependency Injection (DI) is a technique for an object that's being created receive it's dependencies ready for use instead of creating them internally. more about it on the Wiki.

DIPP (Dependency Injection for C++) library aims to be as close to .NET's Microsoft DependencyInjection as possible.

Why is DIPP interesting:

Non intrusive, you can use it with your existing classes.
No auto-registration, you must register your services explicitly.
All services are registered once (using `dipp::service_collection`) with specified descriptor (scope lifetime (transient, scoped or singleton), object's backing memory and dependencies of the object) and will be later on consumed (using `dipp::service_provider`).
Extensible and flexible to define your own service storage, (dipp::service_provider, dipp::service_collection ... are templated storage, defaults to std::map of dipp::move_only_any).

DIPP supports two modes, error based return value using Boost.Leaf and exception throwing when attempting to fetch or add a service (check error\_handling.cpp for examples).

Similar to .NET, DIPP supports keyed services, as in you can instantiate multiple services of the same type with different keys (check keys.cpp for more examples).

struct Engine
{
Window& window1;
Window& window2;

Engine(Window& window1, Window& window2) :
window1(window1), window2(window2)
{
}
};

// Declare our services
using WindowService1 = dipp::injected<Window, ...>;
using WindowService2 = dipp::injected<Window, ..., dipp::key("UNIQUE")>;
using EngineService = dipp::injected<Engine, ..., dipp::dependency<WindowService1, WindowService2>>;

// Create a collection to hold our services
dipp::servicecollection collection;

// add the services to the collection
collection.add<WindowService>();
collection.add<EngineService>();

// create a service provider with the collection
dipp::serviceprovider services(std::move(collection));

// Fetch services
Engine& engine = services.get<EngineService>();

// both window services shouldn't be the same
assert(&engine.window1 != &engine.window2);

Mode info:

Codeberg: [https://codeberg.org/JassJam/dipp.git](https://codeberg.org/JassJam/dipp.git)
Github: https://github.com/JassJam/dipp.git
Basic samples in tests [https://codeberg.org/JassJam/dipp/src/branch/main/tests](https://codeberg.org/JassJam/dipp/src/branch/main/tests)
Somewhat used through out my (incomplete) toy game engine: https://codeberg.org/JassJam/Neko.git

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