blocks|key|1867973|text|好吧，如果我理解的话，你只需要在内部对象发生变化时，用something和somethingelse求和。如果更改是在其中一个对象中进行的，那么您不希望遍历所有其他内部对象。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1867974|好吧，你的$watch没有触发，因为没有stuff.property，也没有像stuff.*.something这样的模式。|1867975|如果您知道对象从数组中推入或拉出的时刻，则可以在将每个对象插入数组之前/之后应用单独的$scope.$watch(object,+function(){},+true)。如果您不知道这一时刻，那么您将需要对整个数组执行$watch操作，当发生更改时，运行所有取消注册函数，然后逐个重新执行$watch操作。|1867976|无论如何，在现在的浏览器中，循环是相当快的，除非你在做繁重的计算，你有数百万个对象(这可能已经是一个内存问题)，你可能会很好地使用它。因此，只有当您有非常繁重的计算时，才有必要分别对它们进行$watch，这可能会影响系统性能。|1867977|entityMap^0|R|9|11|D|0|5|6|K|E|13|H|0|17|15|31|6|40|6|0|2N|6|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|L|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|M|$]]

Well, if I got it, you just want to sum <code>something</code> with <code>somethingelse</code> of the inner objects when they change. And you don't want to loop through all the other inner objects if the change is in one of them.

Well, your <code>$watch</code> isn't firing for there is no <code>stuff.property</code>, and there is no patterns like <code>stuff.*.something</code>.

If you know the moment the objects gets pushed or pulled from the array, than you can apply a separately <code>$scope.$watch(object, function(){}, true)</code> before/after inserting each one to the array. If you don't know this moment, than you will need to <code>$watch</code> the entire array, and when a change happens, run all deregistration functions and <code>$watch</code> them all again, one by one.

Anyway, a loop in nowadays browsers is pretty fast, and except you're doing heavy calculations and you have millions of objects (what would have been a memory problem already) you'll probably be good with it. So, an effort to <code>$watch</code> them all separately is only necessary if you have really heavy calculations, that could comprise the system performance.

blocks|key|2081693|text|在我为你的问题想出了这个解决方案后，我满脸微笑。这个解决方案不仅要观察单个对象，它也不会对求和的其余对象进行完整的循环。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2081694|http://plnkr.co/edit/oPWobcLLtJlxs5vjTYyc?p=preview|offset|length|2081695|app.controller('MainCtrl',+function($scope)+{
++$scope.stuff+=+STUFF;
++var+i;
++$scope.sumOfSomething+=+0;
++$scope.sumOfSomethingElse+=+0;

++for(i=0;i+<+$scope.stuff.length;i%2B%2B+){
++++$scope.$watch('stuff['%2Bi%2B'].something',+function+(newVal,oldVal)+{
++++++//+happens+when+the+watch+is+registered.
++++++if(oldVal+===+newVal){
++++++++$scope.sumOfSomething+%2B=+%2BnewVal;
++++++++return;
++++++}
++++++if(newVal){
++++++++$scope.sumOfSomething+%2B=+%2B+(newVal+-+oldVal);
++++++}
++++});

++++$scope.$watch('stuff['%2Bi%2B'].somethingelse',+function+(newVal,oldVal)+{
++++++//+happens+when+the+watch+is+registered.+
++++++if(oldVal+===+newVal){
++++++++$scope.sumOfSomethingElse+%2B=+%2BnewVal;
++++++++return;
++++++}

++++++if(newVal){
++++++++$scope.sumOfSomethingElse+%2B=+%2B+(newVal+-+oldVal);
++++++}

++++});++
++}
});|code-block|syntax|javascript|2081696|顺便说一句，如果你在STUFF中有大量的对象，我不知道这个解决方案会有多优。此外，如果STUFF中的对象数量要更改，这也不会起作用。我们基本上要做的是使用angular的脏检查循环来为我们做求和。|style|CODE|2081697|还要注意监视侦听器中newVal和oldVal的顺序。您点的菜是错的。|2081698|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1F|0|0|0|A|5|17|5|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@$D|Z|E|10|1|11]]|A|$]]|$1|F|3|G|5|H|7|12|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|13|8|@$D|14|E|15|M|N]|$D|16|E|17|M|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|C]]]]

I am smiling all over the place after I came up with this solution for your problem. Not only is this solution going to watch individual objects, it also is not going to do a complete loop through the rest of the objects for the summation. 

<a href="http://plnkr.co/edit/oPWobcLLtJlxs5vjTYyc?p=preview" rel="nofollow">http://plnkr.co/edit/oPWobcLLtJlxs5vjTYyc?p=preview</a>

<pre><code>app.controller('MainCtrl', function($scope) {
 $scope.stuff = STUFF;
 var i;
 $scope.sumOfSomething = 0;
 $scope.sumOfSomethingElse = 0;

 for(i=0;i &lt; $scope.stuff.length;i++ ){
 $scope.$watch('stuff['+i+'].something', function (newVal,oldVal) {
 // happens when the watch is registered.
 if(oldVal === newVal){
 $scope.sumOfSomething += +newVal;
 return;
 }
 if(newVal){
 $scope.sumOfSomething += + (newVal - oldVal);
 }
 });

 $scope.$watch('stuff['+i+'].somethingelse', function (newVal,oldVal) {
 // happens when the watch is registered. 
 if(oldVal === newVal){
 $scope.sumOfSomethingElse += +newVal;
 return;
 }

 if(newVal){
 $scope.sumOfSomethingElse += + (newVal - oldVal);
 }

 }); 
 }
});
</code></pre>

By the way I dont know how optimal this solution is going to be if you have a large number of objects in <code>STUFF</code>. Also, this wont work as is if the number of objects in <code>STUFF</code> is going to change. What we are basically doing is using the dirty checking loop of angular to do our summation for us. 

Also notice the order of newVal and oldVal in the watch listener. Your order is wrong.

blocks|key|1868008|text|我不会做观察，因为根据您的数组可能有多大，可能会非常繁重。相反，我只需要创建一个过滤器：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1868009|HTML：|1868010|Sum+of+something+is:+{{+stuff+%7C+sum:'something'+}} 
Sum+of+somethingelse+is:+{{+stuff+%7C+sum:'somethingelse'+}}|code-block|syntax|javascript|1868011|Javascript：|1868012|.filter("sum",+function(){
++++return+function(input,+params){
++++++++var+totalSum+=+0;
++++++++for(var+x+=+0;+x+<+input.length;+x%2B%2B){
++++++++++++totalSum+%2B=+input[x][params];
++++++++}
++++++++return+totalSum;
++++}
})|1868013|plnkr：http://plnkr.co/edit/p6kM3ampSuMXnwqcteYd?p=preview|offset|length|1868014|entityMap|0|LINK|mutability|MUTABLE|url|http://plnkr.co/edit/p6kM3ampSuMXnwqcteYd?p=preview^0|0|0|0|0|0|6|1F|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

I would not do a watch as depending on how large your array could be, might be very taxing. Instead I would just create a filter:

HTML:

<pre><code>Sum of something is: {{ stuff | sum:'something' }}&lt;br/&gt;
Sum of somethingelse is: {{ stuff | sum:'somethingelse' }}
</code></pre>

Javascript:

<pre><code>.filter("sum", function(){
 return function(input, params){
 var totalSum = 0;
 for(var x = 0; x &lt; input.length; x++){
 totalSum += input[x][params];
 }
 return totalSum;
 }
})
</code></pre>

plnkr: <a href="http://plnkr.co/edit/p6kM3ampSuMXnwqcteYd?p=preview" rel="noreferrer">http://plnkr.co/edit/p6kM3ampSuMXnwqcteYd?p=preview</a>

blocks|key|2081732|text|由于$watch()采用角度表达式，因此您可以使用自定义观察器函数。在您的例子中，观察变化的最简单方法是简单地将您感兴趣的所有字段相加，然后返回单个数字，这对于angular来说是很好和有效的，并且您的总和将准备好呈现。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2081733|var+sumThings+=+function(obj,+field)+{
++var+val+=+0;
++obj.forEach(function(o)+{
++++val+%2B=+parseInt(o[field]);
++});
++return+val;
};

$scope.$watch(function()+{+return+sumThings($scope.stuff,+"something")},+function+(newVal,+oldVal)+{++++//console.log("watchExpression('something')+fired!",+oldVal,+newVal);
++$scope.somethingSum+=+newVal;
});

$scope.$watch(function()+{+return+sumThings($scope.stuff,+"somethingelse")},+function+(newVal,+oldVal)+{
++$scope.somethingelseSum+=+newVal;
});|code-block|syntax|javascript|2081734|基本上，通过做求和，你就是在做你自己的脏检查。如果您的对象比这里显示的对象更复杂，那么它将比$watch(STUFF,+true)更有效。|2081735|更新的plnkr：http://plnkr.co/edit/d7CvERu3XGkub4l6f1yw?p=preview|2081736|entityMap|0|LINK|mutability|MUTABLE|url|http://plnkr.co/edit/d7CvERu3XGkub4l6f1yw?p=preview^0|2|8|0|0|1A|J|0|9|1F|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|O|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

Since <code>$watch()</code> takes an angular expression you can use a custom watcher function. In your case the easiest way to watch for changes is simply to add up all the fields you're interested in then return a single number which is nice and efficient for angular and your sum will be ready to render.
<pre><code>var sumThings = function(obj, field) {
 var val = 0;
 obj.forEach(function(o) {
 val += parseInt(o[field]);
 });
 return val;
};

$scope.$watch(function() { return sumThings($scope.stuff, &quot;something&quot;)}, function (newVal, oldVal) { //console.log(&quot;watchExpression('something') fired!&quot;, oldVal, newVal);
 $scope.somethingSum = newVal;
});

$scope.$watch(function() { return sumThings($scope.stuff, &quot;somethingelse&quot;)}, function (newVal, oldVal) {
 $scope.somethingelseSum = newVal;
});
</code></pre>
Basically, by doing your summation you're doing your own dirty checking. It'll be more efficient than <code>$watch(STUFF, true)</code> if your objects are more complex than you've shown here.
<h3>Your updated plnkr : <a href="http://plnkr.co/edit/d7CvERu3XGkub4l6f1yw?p=preview" rel="nofollow noreferrer">http://plnkr.co/edit/d7CvERu3XGkub4l6f1yw?p=preview</a></h3>

Basically I want this <a href="http://plnkr.co/edit/3yfXbo1c0llO40HZ8WNP?p=preview">http://plnkr.co/edit/3yfXbo1c0llO40HZ8WNP?p=preview</a> but watch doesn't fire when I change something..

I know that this would have worked

<pre><code>$scope.$watch('stuff', function (newVal, oldVal) {
 console.log(oldVal, newVal);

}, true);
</code></pre>

But since I want to do some summing up inside the watches and I don't want to unnecessarily loop thru or re-sum values that did not change..

//edit - 
note that the plnkr example is just an extraction from the actual app, where you can add and remove rows and much more, like modifying the total number(sum of somethings and somethingelses) from another input outside the ng-repeat..

Angular.js watch only on particular object property

基本上我想要这个，但是当我改变一些东西时，手表不会触发。我知道这是可行的$scope.$watch('stuff', function (newVal, oldVal) {    console.log(oldVal, newVal);}, true);但是，由于我想在手表内部做一些求和，并且我不想不必要地循环遍历或重...

问仅针对特定对象属性的Angular.js监视
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