get and change style property openlayers

Question

i need to change the property of some style after its created, and i need to change it with knowing only the string of the property name. i am getting string like "fillColor" and value like "blue", and i need to change the style object. how can i do it? i didnt find anything in the api. the style code:

            var selectStyle = new OpenLayers.Style({
            externalGraphic: 'styles/tree_selected.png',
            graphicWidth: 16, graphicHeight: 26, graphicYOffset: -24,
            title: 'tree'
        });

Answer 1

If you want to change a style depending on a property of the layer, you can do this by supplying a function as a style context.

Here's an example where the colours were stored in a hash array:

var jobContext = {

    getColour: function (feature, styleEl)
    {
        var jobSector = feature.attributes[<myProperty>];

        return sectorColours[jobSector];
    }
};

To use it, pass in the object, in this case jobContext, to your style:

var ocSketchSymbolizersGeom = {
    "Point": {
        pointRadius: 4,
        graphicName: "circle",
        fillColor: "${getColour}",
        fillOpacity: 1,
        strokeWidth: 1,
        strokeOpacity: 1,
        strokeColor: "${getColour}",
        graphicZIndex: 1
    },
    "Line": {
        strokeWidth: 6,
        strokeOpacity: 1,
        strokeColor: "${getColour}",
        graphicZIndex: 1
    },
    "Polygon": {
        strokeWidth: 2,
        strokeOpacity: 1,
        strokeColor: "${getColour}",
        fillColor: "${getColour}",
        fillOpacity: 0.7,
        graphicZIndex: 1
    }
};


var ocStylesGeom = new OpenLayers.Style(null, { context: jobContext });
ocStylesGeom.addRules([new OpenLayers.Rule({ symbolizer: ocSketchSymbolizersGeom })]);

var markerStyleMap = new OpenLayers.StyleMap(
    { 'default': ocStylesGeom,
      'select': ocStylesGeom
    },
    { extendDefault: true }
);

I can't find examples in the OpenLayers site, but there are more examples on various web sites.