Method getSystem

packages/core/src/ECS/Scene.ts:345–347

* 通过类型获取System实例 * * @param systemType System类型 * @returns System实例，如果未找到则返回null * * @example * ```typescript * const physics = scene.getSystem(PhysicsSystem); * if (physics) { * physics.doSomething(); * } * ```

(systemType: ServiceType<T>)

     * ```
     */
    public getSystem<T extends EntitySystem>(systemType: ServiceType<T>): T | null {
        return this._services.tryResolve(systemType) as T | null;
    }

    /**
     * 标记系统顺序为脏