Migration Guide From 3.x.y series to v4.0.0 - gracicot/kangaru GitHub Wiki

A lot of changes occurred between 3.x.y series and 4.0.0. Many breaking changes has been introduced, and we want the migration to be as smooth as possible.

Class Names

In kangaru 4.0.0, we decided to change the naming convention of classes and aliases. In previous versions of kangaru, it was unclear where PascalCase or snake_case was used.

Now, every classes and aliases tries to follow the naming scheme of the STL and Boost, so classes and aliases are now in snake_case.

Here's a list of all classes and public aliases that changed:

Abstract                    --> abstract
AbstractNotFound            --> abstract_not_found
AbstractService             --> abstract_service
AbstractSharedService       --> abstract_shared_service
AdlMap                      --> (deleted)
All                         --> all
AnyOf                       --> only
AutoCall                    --> autocall
AutoCallNoMap               --> autocall
Container                   --> container
ContainerService            --> container_service
Default                     --> defaults_to
DefaultForkedInvoker        --> forked_invoker
DefaultForkedInvokerService --> forked_invoker_service
DefaultInvoker              --> invoker
DefaultInvokerService       --> invoker_service
Dependency                  --> dependency
FilteredForkService         --> filtered_fork_service
ForkService                 --> fork_service
ForkedGenerator             --> forked_generator
ForkedGeneratorService      --> forked_generator_service
ForkedInvoker               --> forked_mapped_invoker
ForkedInvokerService        --> forked_mapped_invoker_service
ForkedLazy                  --> forked_lazy
ForkedLazyService           --> forked_lazy_service
Generator                   --> generator
GeneratorService            --> generator_service
GenericService              --> generic_service
Inject                      --> inject_t
Invoke                      --> invoke
Invoker                     --> mapped_invoker
InvokerService              --> mapped_invoker_service
Lazy                        --> lazy
LazyService                 --> lazy_service
Map                         --> map_t
NoneOf                      --> except
Overrides                   --> overrides
ServiceType                 --> service_type
Service                     --> service
SharedSrevice               --> shared_service
Single                      --> single
SingleService               --> single_service
UniqueService               --> unique_service

Compatibility Header

If you want to use the newest version of kangaru yet smoothly make the transition from 3.x.y to v4.0.0 in your codebase, you can use the compatibility header.

That header will define a set of aliases with the old class names to the new class names. Simply add #include <kangaru/compatibility.hpp> in your codebase, and that will make your old code still compile in most cases.

Service Map

The service map system has changed drastically. In the 3.x.y series, the service map was a template class, specialized for every function parameter types. In version v3.2.0, we shipped a service map that looked through ADL to find what parameter corresponded to what service. It worked really well and was much easier to use.

To make the ADL map more extensible and more powerful, we decided to make it the only way to map service to parameters. Yet, we wanted to keep the possibility to have many maps to organize services.

So code that used multiple map will have to adapt the service map to use advanced mapping.


struct MyMap1;

struct MyMap2;

struct MyMap1<Class1> : kgr::Map<Class1Service> {};

struct MyMap2<Class2&> : kgr::Map<Class2Service> {};



struct MyMap1;
struct MyMap2;

auto service_map(Class1,  kgr::map_t<MyMap1>) -> Class1Service;
auto service_map(Class2&, kgr::map_t<MyMap2>) -> Class2Service;


Also, note that there's the concept of a default map. So that also changed how global service map worked.


struct MyGlobalMap;

struct MyGlobalMap<Class1> : kgr::Map<Class1Service> {};

struct MyGlobalMap<Class2&> : kgr::Map<Class2Service> {};



auto service_map(Class1)  -> Class1Service;
auto service_map(Class2&) -> Class2Service;


Inspecting The Service Map

Since the service map was defined by the user, one could inspect the service map to know what parameter was mapped to what service.

We now obtain the mapping through ADL, so inspecting the map now require a tool provided by kangaru.


struct MyMap;

struct MyMap<Class> : kgr::Map<ClassService> {};

using MappedService = MyMap<Class>::Service;


struct MyMap;

auto service_map(Class, kgr::map<MyMap>) -> ClassService;

using MappedService = kgr::mapped_service_t<Class, MyMap>;

Note that if the default map is used, we can omit the second parameter: kgr::mapped_service_t<Class>

Generic Service

If you have defined generic services and used kgr::GenericService, you code will break. This is because the generic service has became much simpler, and don't need CRTP anymore.


template<typename, typename = kgr::Dependency<>>
struct MyGenericService;

template<typename T, typename... Deps>
struct MyGenericService<T, kgr::Dependency<Deps...>> : kgr::GenericService<MyGenericService<T, kgr::Dependency<Deps...>>, T> {
    // ...


template<typename, typename = kgr::dependency<>>
struct MyGenericService;

template<typename T, typename... Deps>
struct MyGenericService<T, kgr::dependency<Deps...>> : kgr::generic_service<T> {
    // ...

Note that this change is not needed when using the kangaru/compatibility.hpp header.


The Instance functionality has been removed. Now, or has been replaced by kgr::container::emplace and kgr::container::replace. Thier functionaly is much more clearly defined and prevent misusing the container.

In v4.0.0, you can no longer call the constructor directly, but you can send parameters to the single services construct function using emplace or replace.

If there's something that cannot be possibly done with only emplace or replace, please open an issue and we'll discuss a solution for your case.

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