LoopbackJs Call After Save Operation Hook only once

Question

I have model with createdOn and lastUpdatedOn fields in my PersitedModel which are basically dates.I am updating this on the after save operation hook. This is what MyModel.js looks like.

module.exports = function(MyModel) {
  MyModel.observe('after save', function(ctx, next) {
    if (ctx.instance && ctx.isNewInstance) {
      ctx.instance.updateAttribute('createdOn', new Date());
    }
    if (ctx.instance && !ctx.isNewInstance) {
      ctx.instance.updateAttribute('lastUpdatedOn', new Date());
    }
    next();
 });
}

Now the operation hook keeps calling this method.And Causes my app to crash.

<--- Last few GCs --->

441366 ms: Mark-sweep 1279.7 (1410.5) -> 1279.7 (1410.5) MB, 1093.9 / 0.0 ms [allocation failure] [GC in old space requested].
442456 ms: Mark-sweep 1279.7 (1410.5) -> 1279.7 (1410.5) MB, 1090.7 / 0.0 ms [allocation failure] [GC in old space requested].
443606 ms: Mark-sweep 1279.7 (1410.5) -> 1286.6 (1403.5) MB, 1148.8 / 0.0 ms [last resort gc].
444735 ms: Mark-sweep 1286.6 (1403.5) -> 1293.7 (1403.5) MB, 1129.2 / 0.0 ms [last resort gc].


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 00000173CF3CFB49 <JS Object>

If I remove the code for update of lastUpdatedOn then it works fine.So the problem basically that I am facing is the operation hook keeps calling the method.Is there a way to prevent this.Am I doing something wrong.? I want to call this method only once

Answer 1

For your use-case, you should try using a mixin instead of model hooks. Loopback has some documentation on how you can make your own. There's also one that you can use for this on npm: https://www.npmjs.com/package/loopback-ds-timestamp-mixin