我知道这是一个基本问题...但是我会尽力解释.
I know this is a base question... but I'll try to explain.
我一直在使用Deferred，但有人指出我正在将其用作反模式. 基本上，我可以在子模块中使用deferred.但是，如果这是一个反模式，那么实现此目标的最佳方法是什么，其中子模块"可能不存在..因此，我不想在成功使用父ajax时显式调用子方法打电话.
I've been using a Deferred, but someone pointed out that I'm using it as an anti-pattern. Basically, I can use the deferred in the child module. BUT if this is an anti-pattern, what is the best way to achieve this in which the "child module" might not be there.. SO, I don't want to explicitly call the child method in the success of the parent ajax call.
所以，三个问题:
这是否是一种可行的方法-实现我要追求的目标的好方法是什么?
Is this a viable way, if not - what is a good way to achieve what I am going for?
即使我重置了Deferred，它似乎也没有重置".为什么?
Even though I am resetting the Deferred, it isn't seeming to 'reset'. Why?
CAN也可以通过将其与另一个事件(即onload)耦合来实现. SO ＜我们让ajax和onload做同样的事情.
CAN this also be achieved coupling it with another event - ie, onload. SO< we have the ajax AND onload doing the same thing.
我有一个父模块.
var Z = {}; Z.someVar = $.Deferred(); Z.a = function(){ //methods //Ajax call on page: can be once or multiple calls. $AJAX = { url:..., dataType: ..., //etc.. }.success( function(){ Z.someVar.resolve(); } ).error(); }; // another method that MIGHT exist. Z.b = function(){ var func1 = function(){ // do some stuff Z.someVar = $.Deferred(); // reset it. } Z.someVar.done(function(){ func1(); }) }推荐答案
promise是对单个，一次值计算的抽象.许诺开始待定，然后可以转换为已实现或已拒绝状态.承诺一旦解决(过渡)，便永远无法再更改其状态.
A promise is an abstraction over a single, one time calculation of a value. A promise starts pending, and then can transition to either fulfilled or rejected state. Once a promise resolved (transitioned) it can never change its state again.
递延仅用一种-当您要从不是promise *的东西构造promise时.
Deferreds are used in exactly one - when you want to construct a promise from something that's not a promise*.
在jQuery $.ajax中已经返回一个开始的承诺.
In jQuery $.ajax already returns a promise to begin with.
Z.a = function(){ // this method now returns a promise return $.ajax({...}); };如果要链接它，可以使用.then:
If we want to chain it, we can use .then :
Z.a().then(function(){ // here a() is done. });您还可以使用$.when(大多数promise库中的Promise.resolve)使用缓存模式:
You can also use a caching pattern, using $.when (Promise.resolve in most promise libraries):
Z._a = null; Z.a = function(){ if(z._a){ // already have the value cached: return $.when(z._a); // promise over the value } return $.ajax({...}).then(function(res){ Z._a = res; return res; // chain }); }; Z.b = function(){ return Z.a().then(function(aValue){ // do something with value, your return value here is the resolution // value of the a method call. }); }现在，如果您要等待多个呼叫，则可以将$.when与多个promise一起使用并获取其结果.
Now, if you want to wait for multiple calls, you can use $.when with multiple promises and get their results.
还有其他一些非常罕见的带有聚合的用例
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有没有一种方法可以触发另一个模块中可能“调用"的方法的调用.存在?
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