inversify-cpp

C++17 inversion of control and dependency injection container library.

Dependency Visualization

See the inversify-cpp-visualizer project to generate dependency graphs.

Features

• Constant, dynamic, and automatic resolvers
• Singleton, resolution (TODO), and unique scopes

Documentation

Installation

inversify-cpp supports conan. add inversify-cpp/2.1.0 to your conanfile.py.

view the library on conan center

Scope

Scope manages the uniqueness of a dependency.

Singleton scopes are cached after the first resolution and will be returned on subsequent container.get... calls.

Resolution scopes are cached throughout the duration of a single container.get... call. A dependency tree with duplicate dependencies will resolve each to the same cached value.

By default, the unique scope is used (except for constant values). The unique scope will resolve a unique dependency for each container.get... call.

Integration

#include <mosure/inversify.hpp>

// for convenience
namespace inversify = mosure::inversify;

Examples

Declare Interfaces

struct IFizz {
    virtual ~IFizz() = default;

    virtual void buzz() = 0;
};

using IFizzPtr = std::unique_ptr<IFizz>;

Declare Types

namespace symbols {
    using foo = inversify::Symbol<int>;
    using bar = inversify::Symbol<double>;
    using fizz = inversify::Symbol<IFizzPtr>;
    using fizzFactory = inversify::Symbol<std::function<IFizzPtr()>>;

    using autoFizzUnique = inversify::Symbol<std::function<IFizzUniquePtr>>;
    using autoFizzShared = inversify::Symbol<std::function<IFizzSharedPtr>>;
}

Note: symbols which hold the same interface type may do so via structs which inherit inversify::Symbol

Declare Classes and Dependencies

struct Fizz : IFizz {
    Fizz(int foo, double bar)
        :
        foo_(foo),
        bar_(bar)
    { }

    void buzz() override {
        std::cout << "Fizz::buzz() - foo: " << foo_
                  << " - bar: " << bar_
                  << " - counter: " << ++counter_
                  << std::endl;
    }

    int foo_;
    int bar_;

    int counter_ { 0 };
};

template <>
struct inversify::Injectable<Fizz>
    : inversify::Inject<
        symbols::foo,
        symbols::bar
    >
{ };

Configure Bindings

inversify::Container<
    symbols::foo,
    symbols::bar
> container;

Constant Values

Constant bindings are always singletons.

container.bind<symbols::foo>().toConstantValue(10);
container.bind<symbols::bar>().toConstantValue(1.618);

Dynamic Bindings

Dynamic bindings are resolved when calling container.get....

By default, dynamic bindings have resolution scope (e.g. each call to container.get... calls the factory).

Singleton scope dynamic bindings cache the first resolution of the binding.

container.bind<symbols::fizz>().toDynamicValue(
    [](auto& ctx) {
        auto foo = ctx.container.template get<symbols::foo>();
        auto bar = ctx.container.template get<symbols::bar>();

        auto fizz = std::make_shared<Fizz>(foo, bar);

        return fizz;
    }
).inSingletonScope();

Factory Bindings

Dynamic bindings can be used to resolve factory functions.

container.bind<symbols::fizzFactory>().toDynamicValue(
    [](auto& ctx) {
        return [&]() {
            auto foo = ctx.container.template get<symbols::foo>();
            auto bar = ctx.container.template get<symbols::bar>();

            auto fizz = std::make_shared<Fizz>(foo, bar);

            return fizz;
        };
    }
);

Automatic Bindings

Dependencies can be resolved automatically using an automatic binding. Injectables are a prerequisite to the type being constructed.

Automatic bindings can generate instances, unique_ptr's, and shared_ptr's of a class. The returned type is determined by the binding interface.

container.bind<symbols::autoFizzUnique>().to<Fizz>();
container.bind<symbols::autoFizzShared>().to<Fizz>().inSingletonScope();

Resolving Dependencies

auto bar = container.get<symbols::bar>();

auto fizz = container.get<symbols::fizz>();
fizz->buzz();

auto fizzFactory = container.get<symbols::fizzFactory>();
auto anotherFizz = fizzFactory();
anotherFizz->buzz();


auto autoFizzUnique = container.get<symbols::autoFizzUnique>();
autoFizzUnique->buzz();

auto autoFizzShared = container.get<symbols::autoFizzShared>();
autoFizzShared->buzz();

Running Tests

Use the following to run tests:

bazel run test --enable_platform_specific_config

Note: run the example app in a similar way: bazel run example/simple --enable_platform_specific_config

TODOS

• More compile-time checks
• Resolution scope

Profiling

Run the following to generate a callgrind file:

• bazel run example/profiling --enable_platform_specific_config --compilation_mode=dbg -s
• valgrind --tool=callgrind --dump-instr=yes --simulate-cache=yes --collect-jumps=yes ./bazel-bin/example/profiling/profiling

Containerless Version

See the containerless branch for a static binding (containerless) version of the library.

Generating single_include Variant

Run python ./third_party/amalgamate/amalgamate.py -c ./third_party/amalgamate/config.json -s ./ from the root of the repository.

Thanks

• InversifyJS - API design and inspiration for the project.