Function inject

A function to inject a dependency from a DI (Dependency Injection) container into a variable. This is the actual implementation that handles all overload variants.

Template: T

The original dependency type.

Template: U

The final return type after optional initialization or transformation.

Param: identifier

The identifier used to resolve the dependency.

See

Param: init

Optional: either true to instantiate via constructor, false to skip, or a function to transform the dependency.

Param: isNecessary

If true, throws on failure; if false, returns undefined on resolution or initialization errors.

Returns

The resolved dependency or result of initialization, or undefined if not necessary and resolution fails.

Throws

A DependencyResolutionError if the dependency is not found (and necessary).

Throws

A NoInstantiationMethodError if instantiation is requested but no constructor exists.

Throws

An InitializationError if the initializer throws an error.

Throws

A InjectorError for unknown errors during resolution or transformation.

Example

const service = inject<Service>('Service');

Example

const instance = inject<Service>('Service', true);

Example

const logger = inject<ILogger>('ILogger_', (x) => x.getLogger('Module'), false);
  • inject<T>(identifier): T

  • Resolves a dependency by its identifier without initialization or instantiation.

    Type Parameters

    • T

      The expected type of the dependency.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency from the container.

    Returns T

    The resolved dependency.

    Throws

    A DependencyResolutionError if the dependency is not found.

    Example

    const logger = inject<Logger>('Logger');
  • inject<T>(identifier, shouldInit): T

  • Resolves and instantiates a dependency using its constructor.

    Type Parameters

    • T

      The expected class type of the dependency.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency from the container.

    • shouldInit: true

      Set to true to instantiate the dependency after resolution.

    Returns T

    The resolved and instantiated dependency.

    Throws

    A DependencyResolutionError if the dependency is not found.

    Throws

    A NoInstantiationMethodError if the dependency has no constructor.

    Throws

    An InitializationError if instantiation fails.

    Example

    const instance = inject<Service>('Service', true);
  • inject<T>(identifier, shouldInit, isNecessary): T | undefined

  • Resolves and instantiates a dependency using its constructor, optionally failing silently.

    Type Parameters

    • T

      The expected class type of the dependency.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency from the container.

    • shouldInit: true

      Set to true to instantiate the dependency.

    • isNecessary: false

      If false, resolution or instantiation errors return undefined instead of throwing.

    Returns T | undefined

    The resolved and instantiated dependency, or undefined if resolution or instantiation fails.

    Example

    const instance = inject<Service>('OptionalService', true, false);
    if (instance) instance.doSomething();
  • inject<T>(identifier, shouldInit, isNecessary): T | undefined

  • Resolves a dependency without instantiating it, optionally failing silently.

    Type Parameters

    • T

      The expected type of the dependency.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency from the container.

    • shouldInit: false

      Set to false to skip instantiation.

    • isNecessary: false

      If false, resolution errors return undefined instead of throwing.

    Returns T | undefined

    The resolved dependency, or undefined if not found.

    Example

    const config = inject<Config>('Config', false, false) ?? getDefaultConfig();
  • inject<T, U>(identifier, init): U

  • Resolves a dependency and applies a custom initializer function to transform the result.

    Type Parameters

    • T

      The original dependency type.

    • U

      The final return type after initialization.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency.

    • init: InitDelegate<T, U>

      A function to transform or initialize the dependency.

    Returns U

    The transformed dependency.

    Throws

    A DependencyResolutionError if the dependency is not found.

    Throws

    An InitializationError if the initializer throws.

    Example

    const client = inject<Api>('Api', (api) => api.getClient());
  • inject<T, U>(identifier, init, isNecessary): U | undefined

  • Resolves a dependency and applies a custom initializer function, optionally failing silently.

    Type Parameters

    • T

      The original dependency type.

    • U

      The final return type after initialization.

    Parameters

    • identifier: Identifier

      The identifier used to resolve the dependency.

    • init: InitDelegate<T, U>

      A function to transform or initialize the dependency.

    • isNecessary: false

      If false, resolution or initializer errors return undefined instead of throwing.

    Returns U | undefined

    The transformed dependency, or undefined if resolution or initialization fails.

    Example

    const db = inject<Database, Pool>('Database', (d) => d.getPool(), false);
    if (db) db.query('SELECT * FROM users');

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