OpenLayers label without using StyleMap

Question

I need to show label of each feature based on attribute field value. I know that I can use ${attribute} notation for this purpose. But this approach works only if I make StyleMap and pass it to vector layer constructor. But in this case I can not modify style of each features separately. How I can make layer with labels and with not null value of style property of each feature?

My current config:

var custom_style = {
 fill: true,
 fillColor: "#feb24c",
 fillOpacity: 0.2,
 strokeColor: '#3182bd',
 strokeWidth: 1
};
var l = new OpenLayers.Layer.Vector("Coverage", {
 strategies: [new OpenLayers.Strategy.BBOX()],
 protocol: new OpenLayers.Protocol.HTTP({
 url: "http://***:8088/collect",
 format: new ol.Format.GeoJSON()
 }),
 style: custom_style
});

If I add label: ${attribute} to custom_style object, then text ${attribute} will be shown on map, not value of attribute.

• neogeomat: are you having problems because some features have null value?

Answer 1

If you want to process each feature and display something different depending on the value of a feature attribute, you can supply a function via the style context that returns different values. Here's an example. However, this approach does use a style map - I'm not sure if you want to avoid using one for some reason.

The value of the label is generated by the assigned function.

• Gabor Farkas: Unfortunately, you can't. Variables are only evaluated in StyleMap objects.

Answer 2

In the case of the label, probably this may work:

label: '${attribute}'

Here I modified your code with it:

var custom_style = {
 fill: true,
 fillColor: "#feb24c",
 fillOpacity: 0.2,
 strokeColor: '#3182bd',
 strokeWidth: 1,
 label: '${attribute}'
};
var l = new OpenLayers.Layer.Vector("Coverage", {
 strategies: [new OpenLayers.Strategy.BBOX()],
 protocol: new OpenLayers.Protocol.HTTP({
 url: "http://***:8088/collect",
 format: new ol.Format.GeoJSON()
 }),
 style: custom_style
});

• drnextgis: Unfortunately, this approach doesn't work as I mentioned above.
• Gery: could you post some images showing what you have and what you expect?