Jscex没有xxxAsync().stop()怎么办？

今天一同事问我Jscex怎么没有stop啊？

异步任务就像断线的风筝，我们没法让它说停就停，但是我们在放飞它之前，可以装个定时炸弹。

通常我们可以这样退出一个异步任务：

       var xxxAsync = eval(Jscex.compile("async", function () {
           while (condition) {
               ....
               dosomething
               ....        
               $await(Jscex.Async.sleep(1000));
           }
       }))

通过condition判断是否退出异步任务。或者等同于下面这种方式：

       var xxxAsync = eval(Jscex.compile("async", function () {
           while (true) {
               if(condition)break;
               ....
               dosomething
               ....        
               $await(Jscex.Async.sleep(1000));
           }
       }))

这两种方式的效果是一模一样的。

下面这种方式有个好处就是可以做一些初始化设置什么的：

       var xxxAsync = eval(Jscex.compile("async", function () {
           while (true) {
               if (condition) {
                   //dosomething
                   break;
               }
               //dosomething      
               $await(Jscex.Async.sleep(1000));
           }
       }))

后来，同事又提供了一个要跳出循环的场景

       var xxxAsync = eval(Jscex.compile("async", function () {
           while (true) {
               for (i in XXX) {
                   if (condition) { 
                   //要在这里跳出最外层的循环
                   }
               }
               //dosomething      
               $await(Jscex.Async.sleep(1000));
           }
       }))

所以就只能这样：

       var xxxAsync = eval(Jscex.compile("async", function () {
           while (true) {
               for (i in XXX) {
                   if (condition) {
                       //要在这里跳出最外层的循环
                       breakTag = true;
                   }
               }
               if (breakTag) break;
               //dosomething      
               $await(Jscex.Async.sleep(1000));
           }
       }))

后来同事又提供了一个BT的场景：

       var countAsync1 = eval(Jscex.compile("async", function () {
           while (true) {
               for (i in XXX) {
                   if (condition) {
                       //要在这里跳出最外层的循环
                   }
               }
               $await(Jscex.Async.sleep(1000));
           }
       }))
       var countAsync2 = eval(Jscex.compile("async", function () {
           while (true) {
               for (i in XXX) {
                   if (condition) {
                       //要在这里跳出最外层的循环
                   }
               }     
               $await(Jscex.Async.sleep(1000));
           }
       }))
       
       var executeAsyncQueue = eval(Jscex.compile("async", function () {
           while (true) {
               $await(countAsync1())
               $await(countAsync2())
               $await(Jscex.Async.sleep(1000));
           }

       }))
       executeAsyncQueue().start();

相当于要在异步队列中跳出最最外层的循环。

我给出的方案还是breakTag

       var executeAsyncQueue = eval(Jscex.compile("async", function () {
           while (true) {
               $await(countAsync1())
               $await(countAsync2())
               if (breakTag) break;
               $await(Jscex.Async.sleep(1000));
           }

       }))

同理这个场景也用tag:

        var xxAsync = eval(Jscex.compile("async", function () {
            while (true) {
                //dosomething
                $await(xxxAsync())
                if (breakTag) break;
                $await(Jscex.Async.sleep("1000"));
            }
        }))

        var xxxAsync = eval(Jscex.compile("async", function () {
            if (condition) {
                breakTag = true;
            }
            $await(Jscex.Async.sleep("1000"));

        }))

所以：Jscex没有必要提供stop,你说呢？

Jscex.Async.Task = function (delegate) {
    this._delegate = delegate;
    this._handlers = [];
    this.status = "ready";
}
Jscex.Async.Task.prototype = {
    start: function () {
        if (this.status != "ready") {
            throw 'Task can only be started in "ready" status.';
        }

        var _this = this;

        this.status = "running";
        this._delegate["onStart"](function (type, value) {

            if (_this.status != "running") {
                throw ('Callback can only be used in "running" status.');
            }

            if (type == "success") {

                _this.result = value;
                _this.status = "succeeded";

            } else if (type == "failure") {

                _this.error = value;
                _this.status = "failed";

            } else if (type == "cancel") {

                _this.status = "canceled";

            } else {
                throw ("Unsupported type: " + type);
            }
            
            _this._notify();
        });
    },

    cancel: function () {
        if (this.status != "running") {
            throw 'Task can only be canceled in "running" status';
        }

        var onCancel = this._delegate["onCancel"];
        if (onCancel) onCancel();

        this._notify();
    },

    _notify: function () {
        var handlers = this._handlers;
        delete this._handlers;
        
        for (var i = 0; i < handlers.length; i++) {
            handlers[i](this);
        }
    },

    addListener: function (handler) {
        if (!this._handlers) {
            throw ('Listeners can only be added in "ready" or "running" status.');
        }

        this._handlers.push(handler);
    }
};