injector.ts

import 'reflect-metadata';

/**
 * Every entry point class instance starts its own dependency container.
 * Injector ensures that all decorated classes in the container are singletons.
 */
export class Injector extends Map {

    public resolve<T>(target: Type<any>): T {
        const tokens = Reflect.getMetadata('design:paramtypes', target) || [];
        const injections = tokens.map((token: Type<any>) => this.resolve<any>(token));

        const classInstance = this.get(target);
        if (classInstance) {
            return classInstance;
        }

        const newClassInstance = new target(...injections);
        this.set(target, newClassInstance);

        console.log(`DI-Container created class ${newClassInstance.constructor.name}`);

        return newClassInstance;
    }

    public release(): void {
        for (const value of this.values()) {
            if (typeof value['release'] === 'function') {
                value['release']();
            }
        }

        this.clear();
    }
}