[OpenLayers-Users] Problem with styling vectorfeatures depending on their attributes

[Paul Spencer]

http://trac.openlayers.org/ticket/2146 may help, I filed this a while  
back with a patch to make it possible to use a context and attribute  
map.  This lets you use ${} for feature styling from attributes and  
methods in a context:{} at the same time, reducing the perceived  
overhead of adding a function for every attribute you want to map.  At  
the same time, the patch also modifies what is passed to a context  
function to include the name of the attribute being calculated, which  
means you can use a single function to handle multiple attributes.

This means you can do something like this contrived example:

new StyleMap({
   default: {
     fillColor: "${fillColor}", // should come from feature.attributes
     strokeWidth: "${getStyle}", // should come from getStyle  
function, +2 on attribute value
     strokeColor: "${getStyle}" // should come from getStyle function,  
just strokeColor attribute though.
   },
   context: {
     getStyle: function(feature, attribute) {
       if (attribute == 'strokeWidth') {
         return feature.attributes.strokeWidth + 2;
       } else {
         return feature.attributes[attribute];
       }
   }
});

Not sure if this is useful for you.

Cheers

Paul


On 2009-09-17, at 10:19 AM, Max Stephan wrote:

>
> Hi Andreas,
>
> Thank you for that hint. I already found that out to but it doesn´t  
> help me
> with solving my problem. I prefer to avoid using the context because  
> of
> this. Any other ideas on this?
>
> greets
> Max Stephan
>
> Andreas Hocevar-2 wrote:
>>
>> Max Stephan wrote:
>>> Hi list,
>>>
>>> I have a vectorlayer to which the user can add features and modify  
>>> those
>>> features. The user can change the attributes for the features like
>>> fillColor, strokeColor etc. in a form. A javascript-method is  
>>> executed by
>>> a
>>> button-click and saves those attributes as vectorattributes (e.g.
>>> feature.attributes.fillColor).
>>>
>>> In the styleMap I´m reading those values from the vectorattributes  
>>> to
>>> change
>>> the styling. The stylemap-Code looks like this:
>>> var pointStyleMap = new OpenLayers.StyleMap({
>>> 	"default": new OpenLayers.Style({
>>> 	fillColor: "${fillColor}",
>>> 	fillOpacity: 0.5,
>>> 	strokeColor: "${strokeColor}",
>>> 	strokeWidth: "${strokeWidth}",
>>> 	pointRadius: 10,
>>> 	graphicZIndex: "${graphicZIndex}"
>>> 	}
>>> 	),
>>> 	"select": new OpenLayers.Style({
>>> 	pointRadius: 10,
>>> 	strokeColor: '#FF3333',
>>> 	strokeWidth: "${strokeWidth}"
>>> 	}
>>> 	)
>>> });This works so far. But now I want to add 2 to the strokeWidth  
>>> when the
>>> feature is selected, so I tried it like this:
>>> strokeWidth: "${strokeWidth}" + 2The effect is that the 2 is only
>>> appended
>>> (the code seems to interprete strokeWidth as a String although I  
>>> parsed
>>> it
>>> to an Int via parseInt(), e.g. for a strokeWidth of 2 I get 22 as a
>>> result).
>>> It´s possible to solve this problem by defining a context for the  
>>> style
>>> but
>>> in my opinion that´s a little overkill for such a simple task.
>>> {context:
>>> 	{strokeWidth: function (feature){return  
>>> (feature.attributes.strokeWidth
>>> +
>>> 2)}}
>>> }Now I want to get the pointRadius from the attributes but no matter
>>> which
>>> method I try, it always ends in the error message: "Line: 625  
>>> Column:
>>> 408,
>>> invalid Argument (OpenLayer.js)". Also tried to parse it to an Int  
>>> again
>>> directly in the styleMap .. no effect.
>>> I have to use IE for this project so no further debug information is
>>> available (I´m also not able to install IE8 with it´s debugging  
>>> features
>>> due
>>> to limited admin rights at my workstation).
>>>
>>> Any idea how I could solve this problem?
>>>
>>
>> As soon as you define a context, feature.attributes will no longer be
>> what is available in the template. So you should define your context
>> like this:
>>
>> context: {
>>    strokeWidth: function(feature){...},
>>    strokeColor: function(feature){...},
>>    fillColor: function(feature){...},
>>    graphicZIndex: function(feature){...},
>>    pointRadius: function(feature){...}
>> }
>>
>> Regards,
>> Andreas.
>>
>>> Thx in advance
>>> Max Stephan
>>>
>>>
>>
>>
>> -- 
>> Andreas Hocevar
>> OpenGeo - http://opengeo.org/
>> Expert service straight from the developers.
>>
>> _______________________________________________
>> Users mailing list
>> Users at openlayers.org
>> http://openlayers.org/mailman/listinfo/users
>>
>>
>
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