Function update

packages/core/src/ECS/Systems/EntitySystem.ts:789–815

* 更新系统

()

     * 更新系统
     */
    public update(): void {
        // 检查是否应该处理，并缓存结果供 lateUpdate 使用
        // Check if should process and cache result for lateUpdate
        this._shouldProcessThisFrame = this._enabled && this.onCheckProcessing();

        if (!this._shouldProcessThisFrame) {
            return;
        }

        const monitor = this.getPerformanceMonitor();
        const startTime = monitor.startMonitoring(this._systemName);
        let entityCount = 0;

        try {
            this.onBegin();
            // 查询实体并存储到帧缓存中
            // ReactiveQuery.getEntities() 返回的是安全快照，只在实体变化时才创建新数组
            // ReactiveQuery.getEntities() returns a safe snapshot, only creates new array when entities change
            const entities = this.queryEntities();
            this._entityCache.setFrame(entities);
            entityCount = entities.length;

            this.process(entities);
        } finally {
            monitor.endMonitoring(this._systemName, startTime, entityCount);
        }
    }

    /**
     * 后期更新系统