在实现waitFor方法之前，我们先要搞明白下面这些问题：
1. waitFor方法的形参有限制吗?
没有!如果形参是Task类型,不应该启动Task,如果是function类型,会执行方法.所以waitFor的使用场景应该是waitFor(task1,task2),并且task1,2不知道何时启动(比如是用户点击界面按钮来启动)
2. 关于参数的传递。
var taskExp_0 = new Task(readFile, "123.txt");
var taskExp_1 = new Task(readFile, "aa.txt").start();
var taskExp_2 = new Task(readFile, "bb.txt");
var taskExp_3 = new Task(taskExp_0).waitFor(taskExp_1, taskExp_2).then(writeFile).start();
//taskExp_2模拟不知何时运行的Task,请在控制台运行下面代码
//taskExp_2.start();
上面例子中,taskExp_1,taskExp_2不接收taskExp_0的输出参数,我们希望writeFile可以通过this.Param[0],[1],[2]分别接收taskExp_0,taskExp_1,taskExp_2的输出参数。
明确了这样的设计后，下面是Task.js的实现细节和相关demo，有关waitFor和waitForAny的实现请看注释：
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<script type="text/javascript">
//promise
//读取文件的原始内容
var uploadFile = function (fileName) {
var _this = this;
window.setTimeout(function () {
console.log("uploadFile '" + fileName + "' complete.");
_this.end(fileName);
}, 1800);
};
//读取文件的原始内容
var readFile = function (fileName) {
_fileName = fileName || this.param;
var _this = this;
window.setTimeout(function () {
var rawContent = "xxxxxxxx (" + _fileName + ")";
console.log("read '" + _fileName + "' complete. rawContent is " + rawContent);
_this.end(rawContent);
}, 1000);
};
//请求服务器来解析原始内容,得到真正的内容
var resolveFile = function (serverUrl) {
var _this = this;
var rawContent = _this.param;
window.setTimeout(function () {
var realContent = "Greeting (" + serverUrl + ")";
console.log("resolve file complete. realContent is " + realContent);
_this.end(realContent);
}, 1500);
};
//把真正的内容写入文件
var writeFile = function (fileName) {
var _this = this;
window.setTimeout(function () {
console.log("writeBack1 param[0] is " + _this.param[0] + " ;param[1] is " + _this.param[1]);
_this.end();
}, 2000);
};
var sendMail = function () {
var _this = this;
window.setTimeout(function () {
console.log("sendMail finished");
_this.end();
}, 1000);
}; (function() {
var isFunction = function (target) {
return target instanceof Function;
};
var isArray = function (target) {
return target instanceof Array;
}; //自定义事件管理(代码摘抄自http://www.cnblogs.com/dolphinX/p/3254017.html)
var EventManager = function () {
this.handlers = {};
};
EventManager.prototype = {
constructor: EventManager,
addHandler: function (type, handler) {
if (typeof this.handlers[type] == 'undefined') {
this.handlers[type] = new Array();
}
this.handlers[type].push(handler);
},
removeHandler: function (type, handler) {
if (this.handlers[type] instanceof Array) {
var handlers = this.handlers[type];
for (var i = 0; i < handlers.length; i++) {
if (handler[i] == handler) {
handlers.splice(i, 1);
break;
}
}
}
},
trigger: function (type, event) {
/*
if(!event.target){
event.target = this;
}
*/
if(this.handlers[type] instanceof Array){
var handlers = this.handlers[type];
for(var i=0; i<handlers.length; i++){
handlers[i](event);
}
}
}
}; //所有检测条件返回{result: bool, output: obj}
var Condition = {
then: function(target){
return {result: !!target[0], output: target[0].value};
},
all: function(target){
var output = [];
for(var i=0; i<target.length; i++){
if(target[i]){
output.push(target[i].value);
}
else{
return {result: false};
}
}
return {result: true, output: output};
},
any: function(target){
for(var i=0; i<target.length; i++){
if(target[i]){
return {result: true, output: target[i].value};
}
}
return {result: false};
}
}; //option:{
// autoStart: bool, //自动启动
// keepInputParams: bool //是否把上一步传递过来的input传递给它的下一步
//}
//finishedCallback 表示WorkItem满足条件并结束的回调
var WorkItem = function(arrayArgs, finishedCallback, option){
var _subItems = [];
var _rawOutputParams = [];
//完成WorkItem的检测条件
var _condition;
var _input;
option = option || {};
//增加一个bool类型的属性autoStart,默认值为true,表示当调用_startSubItem时是否自动执行subItem(当subItem是task时根据autoStart参数来执行task,如果subItem是方法时,不管autoStart是什么都会执行)
option.autoStart = option.autoStart !== false;
//是否把上一步传递过来的input传递给它的下一步,默认false
option.keepInput = option.keepInput === true; var _checkFunc = function(args){
if(isFunction(args[0])){
if(args.length == 2 && isArray(args[1])){
_subItems.push({'isFunc': true, 'func': args[0], 'args': args[1]});
}
else{
_subItems.push({'isFunc': true, 'func': args[0], 'args': args.slice(1)});
}
return true;
}
return false;
};
var _checkTask = function(task){
if(task instanceof Task){
_subItems.push({'isFunc': false, 'task': task});
}
};
if(!_checkFunc(arrayArgs)){
for(var i=0; i<arrayArgs.length; i++){
if(!_checkFunc(arrayArgs[i])){
_checkTask(arrayArgs[i]);
}
}
}
_rawOutputParams.length = _subItems.length; var _startSubItem = function(subItemIndex){
var subItem = _subItems[subItemIndex];
if(subItem.isFunc){
var workItemCxt = _getSubItemContext(subItemIndex);
subItem.func.apply(workItemCxt, subItem.args);
}
else{
if(subItem.task.getStatus() == TaskStatus.finished){
_endSubItem(subItem.task.getOutput(), subItemIndex)
}
else{
subItem.task.finished(function(output){
_endSubItem(output, subItemIndex);
});
if(option.autoStart){
subItem.task.start(_input);
}
}
}
};
var _endSubItem = function(output, index){
_rawOutputParams[index] = {
'value': output
};
var testResult = Condition[_condition](_rawOutputParams);
if(testResult.result){
_onFinishedCallback(testResult.output);
}
};
var _merge = function(target, data){
if(data){
if(isArray(data)){
for(var i=0; i<data.length; i++){
target.push(data[i]);
}
}
else{
target.push(data);
}
}
};
var _onFinishedCallback = function(output){
//如果需要保留输入参数,那么需要对输入和输出参数来一个合并
if(option.keepInput){
var result = [];
_merge(result, _input);
_merge(result, output);
if(result.length == 0){
output = undefined;
}
else{
output = result;
}
}
finishedCallback(output)
};
var _getSubItemContext = function(index){
return {
param: _input,
end: function(output){
_endSubItem(output, index);
}
};
}; this.setCondition = function(condition){
_condition = condition;
};
this.start = function(input){
_input = input;
for(var i=0; i<_subItems.length; i++){
_startSubItem(i);
}
};
};
var ConditionWorkItem = function(finishedCallback){
this.start = function(input){
finishedCallback(input);
};
}; var TaskStatus = {
//未开始
pending: 0,
//正在进行
doing: 1,
//已完成
finished: 2
}; window.Task = function(){
var _status = TaskStatus.pending;
var _wItemQueue = [], _currentItem;
var _eventManager = new EventManager();
var _output;
//设置_wItemQueue队列的最后一个WorkItem的完成条件
var _setLastItemCondition = function(condition){
if(condition != null){
var last = _wItemQueue[_wItemQueue.length - 1];
//因为ConditionWorkItem是没有setCondition方法的(它也不需要判断条件),所以有这个if
if(last.setCondition){
last.setCondition(condition);
}
}
};
var _initWorkItem = function(condition, args, option){
_setLastItemCondition(condition);
var item;
if(args.length == 0){
item = new ConditionWorkItem(_finishCallback);
}
else{
var arrayArgs = [];
for(var i=0; i<args.length; i++){
arrayArgs[i] = args[i];
}
item = new WorkItem(arrayArgs, _finishCallback, option);
}
_wItemQueue.push(item);
return item;
};
//WorkItem完成的回调
var _finishCallback = function(output){
var next = _getCurNextItem();
if(next){
//如果有下一个WorkItem,就start它
_currentItem = next;
_currentItem.start(output);
}
else{
//如果没有就通知Task结束
_status = TaskStatus.finished;
_output = output;
_eventManager.trigger("finish", output);
}
};
var _getCurNextItem = function(){
var i=0;
for(; i<_wItemQueue.length; i++){
if(_currentItem == _wItemQueue[i]){
break;
}
}
return _wItemQueue[i + 1];
};
_currentItem = _initWorkItem(null, arguments); this.getStatus = function(){
return _status;
};
this.getOutput = function(){
return _output;
};
this.finished = function(callback){
if(callback){
_eventManager.addHandler("finish", callback);
}
};
this.start = function(input){
if(_status == TaskStatus.pending){
_status = TaskStatus.doing;
//start的时候给最后一个WorkItem设置then条件
_setLastItemCondition("then");
_currentItem.start(input);
}
return this;
};
this.waitFor = function(){
//先初始化一个不会自启动的WorkItem,并且这个WorkItem把上一步传递过来的input传递给它的下一步
//进入这个WorkItem的条件是then,如果你想要进入条件是all,可以这样 xxxxx.all().waitFor(task1).xxxxx
_initWorkItem("then", arguments, {autoStart: false, keepInput: true});
//最后调用all()表示这个WorkItem里面的所有子Item必须都完成才能继续下一步
return this.all();
};
this.waitForAny = function(){
_initWorkItem("then", arguments, {autoStart: false, keepInput: true});
//前面和waitFor的逻辑一样,最后调用any()表示这个WorkItem里面的所有子Item完成其中一个就可以进入下一步
return this.any();
};
this.then = function(){
_initWorkItem('then', arguments);
return this;
};
this.all = function(){
_initWorkItem('all', arguments);
return this;
};
this.any = function(){
_initWorkItem('any', arguments);
return this;
};
};
})(); var taskExp_1 = new Task(readFile, "aa.txt").then(resolveFile, "/service/fileResolve.ashx?file=aa.txt");
var taskExp_2 = new Task(uploadFile, "bb.txt").then(readFile, "bb.txt").then(resolveFile, "/service/fileResolve.ashx?file=bb.txt");
var taskExp_3 = new Task(taskExp_1).waitFor(taskExp_2).then(writeFile, ["cc.txt"]).then(sendMail).start();
//taskExp_2模拟不知何时运行的Task,请在控制台运行下面代码
//taskExp_2.start(); </script>
</body>
</html>