#include <userver/dynamic_config/snapshot.hpp>

Detailed Description

template<typename Variable>
class dynamic_config::Key< Variable >

A config key is a unique identifier for a config variable.

const dynamic_config::Key<bool> kDocStructConfig{"SAMPLE_BOOL_CONFIG", false};

Definition at line 67 of file snapshot.hpp.

Public Types
using	VariableType = Variable
	The type of the parsed config variable.
using	JsonParser = Variable (*)(const formats::json::Value&)
using	DocsMapParser = Variable (*)(const DocsMap&)

Public Member Functions
	Key (std::string_view name, const VariableType &default_value)
	The constructor for a trivial VariableType, e.g. bool, integer, double, string. The default is passed by value.
	Key (std::string_view name, const VariableType &default_value, SchemaHash schema_hash)
	The constructor for a trivial VariableType with schema metadata.
	Key (std::string_view name, DefaultAsJsonString default_json)
	The constructor for a non-trivial VariableType. The default is passed as a JSON string.
	Key (std::string_view name, DefaultAsJsonString default_json, SchemaHash schema_hash)
	The constructor for a non-trivial VariableType with schema metadata.
	Key (std::string_view name, JsonParser parser, DefaultAsJsonString default_json)
	The constructor that provides a special parser from JSON.
	Key (std::string_view name, JsonParser parser, DefaultAsJsonString default_json, SchemaHash schema_hash)
	The constructor with a custom JSON parser and schema metadata.
template<std::size_t N>
	Key (DocsMapParser parser, const ConfigDefault(&default_json_map)[N])
	The constructor that parses multiple JSON config items into a single C++ object.
	Key (ConstantConfig, VariableType value)
	Creates a config that always has the same value.
	Key (const Key &) noexcept=delete
Key &	operator= (const Key &) noexcept=delete
std::string_view	GetName () const noexcept
VariableType	Parse (const DocsMap &docs_map) const
template<typename Variable>
	Key (impl::InternalTag, std::string_view name)
template<typename Variable>
	Key (impl::InternalTag, DocsMapParser parser)

Member Typedef Documentation

◆ DocsMapParser

template<typename Variable>

using dynamic_config::Key< Variable >::DocsMapParser = Variable (*)(const DocsMap&)

Definition at line 73 of file snapshot.hpp.

◆ JsonParser

template<typename Variable>

using dynamic_config::Key< Variable >::JsonParser = Variable (*)(const formats::json::Value&)

Definition at line 72 of file snapshot.hpp.

◆ VariableType

template<typename Variable>

using dynamic_config::Key< Variable >::VariableType = Variable

The type of the parsed config variable.

Definition at line 70 of file snapshot.hpp.

Constructor & Destructor Documentation

◆ Key() [1/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		const VariableType &	default_value )

The constructor for a trivial VariableType, e.g. bool, integer, double, string. The default is passed by value.

Usage example:

const dynamic_config::Key<bool> kDocStructConfig{"SAMPLE_BOOL_CONFIG", false};

Definition at line 222 of file snapshot.hpp.

◆ Key() [2/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		const VariableType &	default_value,
		SchemaHash	schema_hash )

The constructor for a trivial VariableType with schema metadata.

Parameters

schema_hash Opaque schema hash.

Warning: The schema hash must be supplied by code generation. userver treats it as an opaque value and does not calculate it.

Definition at line 227 of file snapshot.hpp.

◆ Key() [3/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		DefaultAsJsonString	default_json )

The constructor for a non-trivial VariableType. The default is passed as a JSON string.

Uses formats::json::Value Parse customization point function to parse VariableType.

Usage example:

// Parser for a type must be defined in the same namespace as the type itself.
// In this example, JSON parser is only needed for dynamic config, so declaring
// it in hpp is not strictly necessary.
SampleStructConfig Parse(const formats::json::Value& value, formats::parse::To<SampleStructConfig>) {
    return SampleStructConfig{
        .is_foo_enabled = value["is_foo_enabled"].As<bool>(),
        .bar_period = value["bar_period_ms"].As<std::chrono::milliseconds>(),
    };
}
 
const dynamic_config::Key<SampleStructConfig>
    kSampleStructConfig{"SAMPLE_STRUCT_CONFIG", dynamic_config::DefaultAsJsonString{R"(
  {
    "is_foo_enabled": false,
    "bar_period_ms": 42000
  }
)"}};

Definition at line 239 of file snapshot.hpp.

◆ Key() [4/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		DefaultAsJsonString	default_json,
		SchemaHash	schema_hash )

The constructor for a non-trivial VariableType with schema metadata.

Parameters

schema_hash Opaque schema hash.

Warning: The schema hash must be supplied by code generation. userver treats it as an opaque value and does not calculate it.

Definition at line 244 of file snapshot.hpp.

◆ Key() [5/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		JsonParser	parser,
		DefaultAsJsonString	default_json )

The constructor that provides a special parser from JSON.

Warning: Prefer the constructors above whenever possible.

Can be used when generic Parse is not applicable. Sometimes used to add validation, e.g. minimum, maximum, string pattern, etc.

Definition at line 256 of file snapshot.hpp.

◆ Key() [6/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	std::string_view	name,
		JsonParser	parser,
		DefaultAsJsonString	default_json,
		SchemaHash	schema_hash )

The constructor with a custom JSON parser and schema metadata.

Parameters

name	config variable name
parser	custom JSON parser for the variable
default_json	default value as a JSON string
schema_hash	Opaque schema hash. Stored in the global registry and retrievable via dynamic_config::impl::GetRegisteredConfigsMeta() as dynamic_config::RegisteredConfigMeta::schema_hash.

Warning: The schema hash must be supplied by code generation. userver treats it as an opaque value and does not calculate it.

Definition at line 261 of file snapshot.hpp.

◆ Key() [7/10]

template<typename Variable>

template<std::size_t N>

dynamic_config::Key< Variable >::Key	(	DocsMapParser	parser,
		const ConfigDefault(&)	default_json_map[N] )

The constructor that parses multiple JSON config items into a single C++ object.

To register schema metadata for the JSON config items, pass the generated variable_namespace::GetSchemaHash() to each ConfigDefault.

Warning: Prefer to use a separate Key per JSON config item and use the constructors above whenever possible.

Definition at line 274 of file snapshot.hpp.

◆ Key() [8/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	ConstantConfig	,
		VariableType	value )

Creates a config that always has the same value.

Definition at line 293 of file snapshot.hpp.

◆ Key() [9/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	impl::InternalTag	,
		std::string_view	name )

Definition at line 298 of file snapshot.hpp.

◆ Key() [10/10]

template<typename Variable>

dynamic_config::Key< Variable >::Key	(	impl::InternalTag	,
		DocsMapParser	parser )

Definition at line 308 of file snapshot.hpp.

Member Function Documentation

◆ GetName()

template<typename VariableType>

std::string_view dynamic_config::Key< VariableType >::GetName ( ) const

noexcept

Returns: the name of the single registered config item, or the explicit name of an internal derived key. Calling this for a key with zero or multiple config items and no explicit internal name is an invariant violation.

Definition at line 316 of file snapshot.hpp.

◆ Parse()

template<typename VariableType>

VariableType dynamic_config::Key< VariableType >::Parse ( const DocsMap & docs_map ) const

Parses the config. Useful only in some very niche scenarios. The config value should be typically be retrieved from dynamic_config::Snapshot, which is obtained from components::DynamicConfig in production or from dynamic_config::StorageMock in unit tests.

Definition at line 321 of file snapshot.hpp.

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

userver/dynamic_config/fwd.hpp
userver/dynamic_config/snapshot.hpp

Detailed Description

Public Types

Public Member Functions

Member Typedef Documentation

◆ DocsMapParser

◆ JsonParser

◆ VariableType

Constructor & Destructor Documentation

◆ Key() [1/10]

◆ Key() [2/10]

◆ Key() [3/10]

◆ Key() [4/10]

◆ Key() [5/10]

◆ Key() [6/10]

◆ Key() [7/10]

◆ Key() [8/10]

◆ Key() [9/10]

◆ Key() [10/10]

Member Function Documentation

◆ GetName()

◆ Parse()