components::Container< T > Class Template Reference

#include <userver/components/container.hpp>

Detailed Description

template<typename T>
class components::Container< T >

A simple Component that creates, hold, and distributes an object of user type T. The component has a name equal to the constexpr std::string_view result of user-defined ContainerName(Of<T>{}).

Every dependency of type X is resolved by the component using components::LocateDependency. By default, it is able to resolve the following types of dependencies:

• X that was previously registered via defining ContainerName(Of<X>). That is a containerized dependency.
• X that declares Parse(const yaml_config::YamlConfig& value, formats::parse::To<X>). This is a static config dependency.

Besides that, you may define our own specialization for components::LocateDependency to allow fetching dependencies from non-container components. E.g. userver already defines dynamic_config::Source from components::DynamicConfig.

The core limitation of a type T registered via ContainerName(Of<T>) is that it is not able to explicitly use components::ComponentContext in the consturctor. But if you want to only "fetch" something from the context, you're always able to define your own components::LocateDependency that fetches everything you need from components::ComponentContext.

Example:

// A simple containerized type
struct X {
    // Default ctr => the container creates `X` with no external dependencies
    X() = default;
    X(const X&) = delete;
};
 
// Register a container with name "x" that stores an object of type X
constexpr std::string_view ContainerName(components::Of<X>) { return "x"; }
 
// A containerized type that has a dependency of type `X`
struct Y {
    // Container<Y> will use a dependency of type `X`.
    // `X` is a containerized type, so it will be searched by
    // `FindComponent<Container<X>>().Get()`.
    Y(X&) {}
};
 
// Register a container with name "y" that stores an object of type Y
constexpr std::string_view ContainerName(components::Of<Y>) { return "y"; }

    // Register all containerized types in the component system as `Container<T>`
    auto component_list =
        components::MinimalComponentList()  //
            .Append<components::Container<X>>()
            .Append<components::Container<Y>>();

Definition at line 144 of file container.hpp.

Inheritance diagram for components::Container< T >:

Public Member Functions
	Container (const ComponentConfig &config, const ComponentContext &context)
T &	Get ()
ComponentHealth	GetComponentHealth () const override
void	OnLoadingCancelled () override
void	OnAllComponentsLoaded () override
void	OnAllComponentsAreStopping () override

Static Public Member Functions
static yaml_config::Schema	GetStaticConfigSchema ()

Static Public Attributes
static constexpr auto	kConfigFileMode = ConfigFileMode::kNotRequired
static constexpr std::string_view	kName = impl::GetContainerName<T>()

Protected Types
using	LoggableComponentBase = ComponentBase

Member Typedef Documentation

LoggableComponentBase

using components::ComponentBase::LoggableComponentBase = ComponentBase

protectedinherited

Deprecated:

use components::ComponentBase instead.

Definition at line 67 of file component_base.hpp.

Constructor & Destructor Documentation

Container()

template<typename T >

components::Container< T >::Container ( const ComponentConfig &  config, const ComponentContext &  context  )

inline

Definition at line 146 of file container.hpp.

Member Function Documentation

Get()

template<typename T >

T & components::Container< T >::Get ( )

inline

Definition at line 151 of file container.hpp.

GetComponentHealth()

ComponentHealth components::ComponentBase::GetComponentHealth ( ) const

inlineoverridevirtualinherited

Override this function to inform the world of the state of your component.

Warning

The function is called concurrently from multiple threads.

Reimplemented from components::RawComponentBase.

Reimplemented in server::handlers::Restart.

Definition at line 35 of file component_base.hpp.

GetStaticConfigSchema()

static yaml_config::Schema components::ComponentBase::GetStaticConfigSchema ( )

staticinherited

If the component pulls more options from components::ComponentConfig than its parent component, then it needs to define GetStaticConfigSchema method and add its own options to the parent component's options.

Examples

libraries/easy/samples/4_custom_dependency/main.cpp, and libraries/easy/samples/5_pg_service_template/src/main.cpp.

OnAllComponentsAreStopping()

void components::ComponentBase::OnAllComponentsAreStopping ( )

inlineoverridevirtualinherited

Component may use this function to stop doing work before the stop of the components that depend on it.

Base components may override it and make final to do some work before the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, and components::Server.

Definition at line 58 of file component_base.hpp.

OnAllComponentsLoaded()

void components::ComponentBase::OnAllComponentsLoaded ( )

inlineoverridevirtualinherited

Component may use this function to finalize registration of other components that depend on it (for example, handler components register in server component, and the latter uses OnAllComponentsLoaded() to start processing requests).

Base components may override it and make final to do some work after the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, components::Server, and server::handlers::Ping.

Definition at line 51 of file component_base.hpp.

OnLoadingCancelled()

void components::ComponentBase::OnLoadingCancelled ( )

inlineoverridevirtualinherited

Called once if the creation of any other component failed. If the current component expects some other component to take any action with the current component, this call is a signal that such action may never happen due to components loading was cancelled. Application components might not want to override it.

Reimplemented from components::RawComponentBase.

Definition at line 42 of file component_base.hpp.

Member Data Documentation

kConfigFileMode

template<typename T >

constexpr auto components::Container< T >::kConfigFileMode = ConfigFileMode::kNotRequired

staticconstexpr

Definition at line 153 of file container.hpp.

kName

template<typename T >

constexpr std::string_view components::Container< T >::kName = impl::GetContainerName<T>()

staticconstexpr

Definition at line 155 of file container.hpp.

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The documentation for this class was generated from the following file:

• userver/components/container.hpp