[mapserver-dev] Using updateFromString on existing items

[Tamas Szekeres]

Adding a separate function is fine for me. Would that be easy to implement?
I've been thinking that freeLayer would do the trick, but that is bound to
a reference counting approach, which prevents from calling this method in
my use case.

Tamas


2017-10-10 20:36 GMT+02:00 Lime, Steve D (MNIT) <steve.lime at state.mn.us>:

> I was thinking more about this and I think there are several possibilities
> if you want to completely repopulate a layer (or other object) from a
> string. Personally, I’d leave the updateFromString() method alone and add a
> reset/init or whatever method that basically free’s the object and then
> re-initializes it resulting in an object that is ready to load a definition
> into. For a layer that would clear out projections, classes, etc…, for a
> class that would clear out styles, and so on… Code would look something
> like:
>
>
>
>   $layer = $map->getLayerByName(‘foo’);
>
>   $layer->reset();
>
>   $layer->updateFromString($fullLayerDefinitionString);
>
>
>
> One could also add new method to explicitly do the reset and update (e.g.
> resetFromString) or perhaps add a flag to the updateFromString method to
> reset.
>
>
>
> Steve
>
>
>
> *From:* mapserver-dev [mailto:mapserver-dev-bounces at lists.osgeo.org] *On
> Behalf Of *Lime, Steve D (MNIT)
> *Sent:* Monday, October 09, 2017 11:12 AM
> *To:* Tamas Szekeres <szekerest at gmail.com>
>
> *Cc:* mapserver-dev at lists.osgeo.org
> *Subject:* Re: [mapserver-dev] Using updateFromString on existing items
>
>
>
> I think we need to spend a little time looking at the code and the
> original RFC to properly document the “as is” behavior and then determine
> if any changes are necessary. Looking at the layer code I think my
> reference to “minor edits” is wrong. If you update a layer from a string in
> MapScript and that string contains classes then **new** classes are added
> to the layer object. If you want to update an existing class you’d have to
> update it directly from a string, not via the parent layer. Resetting the
> object would be a pretty drastic change. It may be that only projections
> need some sort of intervention to clear things out…
>
>
>
> Steve
>
>
>
> *From:* Tamas Szekeres [mailto:szekerest at gmail.com <szekerest at gmail.com>]
> *Sent:* Monday, October 09, 2017 10:18 AM
> *To:* Lime, Steve D (MNIT) <steve.lime at state.mn.us>
> *Cc:* mapserver-dev at lists.osgeo.org
> *Subject:* Re: [mapserver-dev] Using updateFromString on existing items
>
>
>
> Hi Steve,
>
>
>
> It is hard to interpret what are the allowed "minor edits" in such case.
> Neither the documentation or the corresponting rfc provides any guidance.
>
> One can think a reasonable use case to completely deserialize the object
> state by using these methods.
>
>
>
> Do we have a simple approach to reset the state of the object (as it was
> newly created) before calling the updateFromString method?
>
>
>
> Thanks,
>
>
>
> Tamas
>
>
>
>
>
>
>
> 2017-10-09 16:23 GMT+02:00 Lime, Steve D (MNIT) <steve.lime at state.mn.us>:
>
> The original use case was to facilitate minor edits to existing object
> properties but not sub-objects. For example, you can't replace all the
> classes in a layer through a string update to the layer itself. We
> certainly could make all that work cleaner if there were demand.
>
> At least you get a proper error message... ;-)
>
>
>
> Steve
> ------------------------------
>
> *From:* mapserver-dev <mapserver-dev-bounces at lists.osgeo.org> on behalf
> of Tamas Szekeres <szekerest at gmail.com>
> *Sent:* Sunday, October 8, 2017 12:49:55 PM
> *To:* mapserver-dev at lists.osgeo.org
> *Subject:* [mapserver-dev] Using updateFromString on existing items
>
>
>
> Hi Devs,
>
>
>
> Is that a supported use case to apply updateFromString on an existing item
> or it should only be used only on a newly created item?
>
>
>
> For example when I use layerObj.updateFromString on an existing layer I
> get the following error
>
>
>
> loadProjection(): General error message. Projection is already
> initialized. Multiple projection definitions are not allowed in this
> object. (line 10)
>
>
>
> This is because we don't have a proper cleanup code on the existing layer
> before calling loadLayer on it. The same applies to the other object types.
>
>
>
> Thanks,
>
> Tamas
>
>
>
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