@typemon/reflection

Reflection -

• Parameter metadata management
• Inheritance support
• Easy integration with decorators

Installation

$ npm install @typemon/reflection reflect-metadata

TypeScript

• Version 3.5 or later is required.
• Configure the decorator and metadata options.
  • https://www.typescriptlang.org/docs/handbook/decorators.html#metadata

{
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true
}

Reflect Metadata

• Import only once at application entry point.

import 'reflect-metadata';

Usage

• Reflection
• Metadata
• Metadata Decorator

Reflection

Reflection.hasOwnMetadata(metadataKey, target, propertyKey?): boolean;
Reflection.hasNotOwnMetadata(metadataKey, target, propertyKey?): boolean;
Reflection.hasMetadata(metadataKey, target, propertyKey?): boolean;
Reflection.hasMetadata(metadataKey, target, propertyKey?): boolean;
Reflection.getOwnMetadata(metadataKey, target, propertyKey?): any;
Reflection.getMetadata(metadataKey, target, propertyKey?): any;
Reflection.setMetadata(metadataKey, metadataValue, target, propertyKey?): void;
Reflection.deleteMetadata(metadataKey, target, propertyKey?): void;
Reflection.decorate(decorators, {
    target,
    propertyKey?,
    parameterIndex?
}): void;
Reflection.DefineMetadata(metadataKey, metadataValue): ClassDecorator & PropertyDecorator & MethodDecorator;

Metadata

Metadata.of({
    target,
    propertyKey?,
    parameterIndex?
}): Metadata;
Metadata.hasOwn(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): boolean;
Metadata.hasNotOwn(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): boolean;
Metadata.has(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): boolean;
Metadata.hasNot(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): boolean;
Metadata.getOwn(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): any;
Metadata.get(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): any;
Metadata.set(metadataKey, metadataValue, {
    target,
    propertyKey?,
    parameterIndex?
}): void;
Metadata.delete(metadataKey, {
    target,
    propertyKey?,
    parameterIndex?
}): void;

Metadata Decorator

You can easily set metadata using the Metadata.Define decorator.

@Metadata.Define(metadataKey, metadataValue)
class Target {
    @Metadata.Define(metadataKey, metadataValue)
    public static staticProperty: unknown;

    @Metadata.Define(metadataKey, metadataValue)
    public static staticMethod(
        @Metadata.Define(metadataKey, metadataValue)
        staticMethodParameter: unknown
    ): void { }

    @Metadata.Define(metadataKey, metadataValue)
    public instanceProperty: unknown;

    public constructor(
        @Metadata.Define(metadataKey, metadataValue)
        constructorParameter: unknown
    ) { }

    @Metadata.Define(metadataKey, metadataValue)
    public instanceMethod(
        @Metadata.Define(metadataKey, metadataValue)
        instanceMethodParameter: unknown
    ): void { }
}

You can create and use custom decorators as needed.

function CustomDecorator(): Metadata.Decorator {
    return Metadata.Decorator.create((metadata: Metadata): void => {
        . . .
    });
}