On 20 Apr 2011, at 16:44, Patrick Barnes wrote:
> Actually, he is...
>
> if doc.events is an object, then the object might not actually be copied, but
> only a reference.
I understand that it is a reference, but my shell example supports my
understanding of the copy on write semantics (which still may be wrong :)
Cheers
Jan
--
>
> If you change
> var events = doc.events;
> to
> var events = clone doc.event;
>
> Does that fix it?
>
> On 20/04/2011 10:59 PM, Jan Lehnardt wrote:
>>
>> On 20 Apr 2011, at 14:11, Nils Breunese wrote:
>>
>>> Hello all,
>>>
>>> I recently upgraded to CouchDB 1.0.2 for development and found some of our
>>> view map functions broke. Apparently it's no longer possible to modify data
>>> a doc in a view function before emitting. I found "Documents are now sealed
>>> before being passed to map functions." in the changelog for 1.0.2.
>>>
>>> This is an example of a map function which no longer works under 1.0.2:
>>>
>>> ----
>>> function(doc) {
>>> if(doc.type === 'schedule') {
>>> var events = doc.events;
>>> if (events) {
>>> events.forEach(function(event) {
>>> var broadcasters = event.broadcasters;
>>> if (broadcasters) {
>>> broadcasters.forEach(function(broadcaster) {
>>> if(broadcaster === 'VPRO') {
>>> event.channel = doc.channel;
>>> event.channelName = doc.channelName;
>>> emit(event.end, event);
>>> }
>>> });
>>> }
>>> });
>>> }
>>> }
>>> }
>>> This creates a deep copy before modifying event properties. It works, but
>>> it looks ugly to me. Is this the way to go or is there a cleaner way?
>>
>> I use JSON.parse(JSON.stringify(doc)) but that is essentially the same :)
>>
>> The reason that doc modifications work were an artefact of a bug in
>> Spidermonkey that finally got resolved. You shouldn't rely on being able to
>> modify a doc in map functions.
>>
>> That said, I'm surprised you get this error as you are not assigning
>> anything do doc.events. Unless I got wrong how chaining in JS works, this
>> shouldn't be a problem:
>>
>> js> var a = {a:1};
>> js> seal(a);
>> js> a.a = 2;
>> typein:4: Error: a.a is read-only
>> js> var b = a.a;
>> js> print(b);
>> 1
>> js> b = 2
>> 2
>> js>
>>
>> Cheers
>> Jan
