Skirnir

Skirnir provides an IoC Container. It uses The C++ Type Loophole to get constructor parameters and to allow registering services for dependency injection

Lifetimes

Skirnir is inspired by the Microsoft dependency injection.

Lifetime	Description
Transient	is instantiated at each invocation
Scoped	is instantiated only once per scope, then it is obtained through the scope cache
Singleton	is instantiated only once in the entire application as long as another root service provider is not created.

Usage

Concrete type

Start by creating the ServiceCollection and add your services by the concrete types.

    auto serviceCollection = skr::ServiceCollection();

    serviceCollection.AddSingleton<Singleton>();
    serviceCollection.AddScoped<Scoped>();
    serviceCollection.AddTransient<Transient>();

Interface/Contract

    auto serviceCollection = skr::ServiceCollection();

    serviceCollection.AddSingleton<ISingleton, Singleton>();
    serviceCollection.AddScoped<IScoped, Scoped>();
    serviceCollection.AddTransient<ITransient, Transient>();

Injecting

class Scoped {
public:
    Scoped(Ref<ITransient> transient) : mTransient(transient) {}
private:
    Ref<ITransient> mTransient;
};

Logging

Skirnir uses the fmt to provide global logging capabilities, every service added will also add a skr::Logger<TService>. This logger can be injected and produces logging messages with the typename of the template argument:

class Repository : public IRepository
{
  public:
    Repository(Ref<skr::Logger<Repository>> logger) : mLogger(logger) {}
    ~Repository() override = default;

    void Add() override { mLogger->LogInformation("Add"); }

  private:
    Ref<skr::Logger<Repository>> mLogger;
};

Calling the Repository::Add() method will output:

[Information] 2025-03-12 21:55:19.650921540 'Repository': Add