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From: Nils Breunese <N.Breunese@vpro.nl>
To: "user@couchdb.apache.org" <user@couchdb.apache.org>
Date: Thu, 21 Apr 2011 14:08:31 +0200
Subject: Re: Dealing with sealed docs
Thread-Topic: Dealing with sealed docs
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Patrick Barnes wrote:

> My apologies - I have mis-remembered. No, there is no clone operator,
> but some functions will return a copy rather than a reference.
>
> I had a view that looked like:
> function(doc) {
>         if (doc.status=3D=3D'active' && doc.doc_type=3D=3D'group') {
>                 doc.path.pop();
>                 emit(doc.path, doc.display_name);
>         }
> }
> And it (on pre-1.0.2 couchdb) failed to generate the views properly,
> because doc.path.pop() was modifying the doc and the next views were
> receiving that modified version.
>
> In my case, changing the view to this fixed it:
> function(doc) {
>         if (doc.status=3D=3D'active' && doc.doc_type=3D=3D'group') {
>                 path =3D doc.path.slice(0);
>                 path.pop();
>                 emit(path, doc.display_name);
>         }
> }
>
> So doc.path.slice(0) copies the whole doc.path array for me so that I
> can modify it before emitting. No such neat method exists for objects
> unfortunately, but how about:
>
> function(doc) {
>   if(doc.type =3D=3D=3D 'schedule') {
>     var events =3D doc.events;
>     if (events) {
>       events.forEach(function(event) {
>         var broadcasters =3D event.broadcasters;
>         if (broadcasters) {
>           broadcasters.forEach(function(broadcaster) {
>             if(broadcaster =3D=3D=3D 'VPRO') {
> -              event.channel =3D doc.channel;
> -              event.channelName =3D doc.channelName;
> -              emit(event.end, event);
> +              var _event =3D {channel:doc.channel,
> channelName:doc.channelName};
> +              for (var k in event) _event[k]=3Devent[k];
> +              emit(event.end, _event);
>             }
>           });
>         }
>       });
>     }
>   }
> }
>
> The members of _event are only references, but that should be okay
> because you're not modifying those, only adding two extra attributes to
> the new object created. (Not having to _copy_ every element should also
> make this approach much faster than using a generic 'clone' method)
>
> Hope that works. :-)

Thanks, I'm using this approach now and it seems to work.

Nils.
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