Is using ng-init for bind once valid in angular js?

Question

i have a collection of values whose structure lets assume to be

var a = [{id:1, value:12, name="one"}, {id:2, value:34, name="two"},...]

i wanted to display this in a series of controls so that user can change the values. but with that i also wanted to display original values which obviously shoudn't change.
i found out a way that is working and my code is something like this using ng-init

 <div ng-repeat="p in a">
  <div class="control-group" ng-if="p.value>0">
    <label class="control-label" ng-bind="p.name"></label>
    <div class="controls controls-row" ng-init="v=p.value">
      <input class="span1" value="{{v}}"/>
      <input type="number" ng-model="p.value" class="span2" />
    </div>
  </div>
</div>

being a complete newbie in angularjs i dont know what implications this might have as i have very little experience in thinking about $watch and performance.

Is it ok to do so?

would suggest just copying the whole array if you want to keep it...`var b= angular.copy(a)`. Can then match indexes for markup — charlietfl, Nov 29 '13 at 06:22
@charlietfl - yes my first attempt was that. but still angular keeps watching the values when i know they wont be changing. — Parv Sharma, Nov 29 '13 at 06:24
at first i did that.. to copy the array and then using it to bind values. But still if i cope an array using angular.copy() it creates a deep copy and hence angular js will continue to look for changes — Parv Sharma, Nov 29 '13 at 09:47
you keep saying the same thing....and it's not making sense. A demo would help that presents your issue — charlietfl, Nov 29 '13 at 14:18

Maxim Shoustin · Accepted Answer · 2013-11-29T07:03:27.823

0

but with that i also wanted to display original values which obviously shoudn't change.

Use angular.copy(/* array */). It will create new copy (instance) of old array.

BTW a collection must be defined as $scope.a

Demo Fiddle

edited Nov 29 '13 at 07:03

answered Nov 29 '13 at 06:57

Maxim Shoustin

77,483
27
203
225

this is not my question. deep copying an array and then displaying a value is ok but what about using ng-init? – Parv Sharma Nov 29 '13 at 07:55
can you post your `watch` method? I don't undersend `ng-init="v=p.value` goal. it does nothing, but creates new value `v` – Maxim Shoustin Nov 29 '13 at 09:29
i have no watch method, the value created here is what im using later to display – Parv Sharma Nov 29 '13 at 09:36
but you can write: `value="{{p.value}}"` its the same. Do you want to prevent deep watch on `p` by creating new `v`? it will not help you, in your case v = p.value. – Maxim Shoustin Nov 29 '13 at 09:40
yes i want to prevent deep watch. and it is not equal to value={{p.value}} because if i use {{p.value}} then if the p.value changes later value of the input changes – Parv Sharma Nov 29 '13 at 09:48
so write `v = angular.copy(p.value)` – Maxim Shoustin Nov 29 '13 at 09:59

Is using ng-init for bind once valid in angular js?

1 Answers1