OpenLayers 2 Cluster - style rules 'property' value

Question

I am using a cluster vector layer and have a doubt about the value of 'property' in rule.

My code is:

 rules: [
    new OpenLayers.Rule({
        filter: new OpenLayers.Filter.Comparison({
        type: OpenLayers.Filter.Comparison.EQUAL_TO,
        property: "amount", 
        value: 1
        }),
        symbolizer: {
        fillColor: '#34f2f9'
        }
    }),
    new OpenLayers.Rule({

        elseFilter: true,
        symbolizer: {
        fillColor: '#fff'
        }
    })
 ]

My doubt is how to get the value of amount in the above code. From where I will pass the value of amount .

Whole code for adding layer is:

function rqstSubmit(params,url) {  

if (featureSubVector){
    featureSubVector.removeAllFeatures(); 
    map.removeLayer(featureSubVector);  
    featureSubVector = null;    
} 
var style = new OpenLayers.Style(
    { 
       rules: [
        new OpenLayers.Rule({
            filter: new OpenLayers.Filter.Comparison({
            type: OpenLayers.Filter.Comparison.EQUAL_TO,
            property: 'amount', 
            value: 1
            }),
            symbolizer: {
            fillColor: '#34f2f9', 
            pointRadius: '10',
            fillOpacity: 0.6,  
            strokeColor: '#cc6633',
            label: "${getLabel}"
            }
        }),
        new OpenLayers.Rule({
            elseFilter: true,
            symbolizer: {
            fillColor: '#fff', 
            pointRadius: '10',
            fillOpacity: 0.6,  
            strokeColor: '#cc6633',
            label: "${getLabel}"
            }
        })
       ]
    }, 

    { 
      context: { 
        getLabel: function(feature) { 
        if (feature.cluster) {
            if (feature.cluster.length > 1) {
            return feature.cluster.length;
            }
        }
        return '';
        }
      }
}); 

var featureSubVector = new OpenLayers.Layer.Vector('Search Result', {
    strategies: [
    new OpenLayers.Strategy.Cluster()
    ],
    styleMap: new OpenLayers.StyleMap({
    'default': style,
    'select': {fillColor: '#8aeeef'}
    })      
});

map.addLayer(featureSubVector);  

PDGeoJsonFormat=new OpenLayers.Format.GeoJSON();
PDRequest.open('POST',/some/url/,true);
    PDRequest.onreadystatechange=function(){
   if(PDRequest.readyState==4 && PDRequest.status==200){
   if(PDGeoJsonFormat.read(PDRequest.responseText)!=null){
    PDJsonFeatures=PDGeoJsonFormat.read(PDRequest.responseText);

    if(PDJsonFeatures.length > 0){
           content="";

           for(i=0;i<PDJsonFeatures.length;i++) {   
        content = content+"<tr> <td align='center'  style='width:35px;'>"+(i+1)+"</td><td  href='javascript:void(0);'  onClick=\"ResultZoomLoc('"+ PDJsonFeatures[i].attributes['title']+"','"+PDJsonFeatures[i].attributes['name']+"','"+PDJsonFeatures[i].attributes["x"]+"','"+ PDJsonFeatures[i].attributes["y"]+"','"+ PDJsonFeatures[i].attributes['amount'] +"')\" >"+ PDJsonFeatures[i].attributes['nameUnit']+"</td></tr>";    
       }    

     var ulcontent = '<table width="99%" align="center"><tr style="background:#aed6e8;"> <th colspan="2">RESULT ('+PDJsonFeatures.length+')</th></tr>   '+content+' </table>';  
    $("#result").html(ulcontent); //--append result to popup div--

    featureSubVector.removeFeatures(PDJsonFeatures);
    PDJsonFeatures = PDGeoJsonFormat.read(PDRequest.responseText);
    var selectControl = new OpenLayers.Control.SelectFeature(featureSubVector,{clickout: true, toggle: false, multiple: false, hover: false });

    featureSubVector.events.on({ 
        "featureselected": clusterClick, //--Function-on-cluster-click--
        "featureunselected": ClusterCloseCloud //--Function-on-close--
    });

    map.addControl(selectControl); 
    selectControl.activate(); 
    featureSubVector.addFeatures(PDJsonFeatures); 

    }       
    else  dispErrMessage("error_popup","No data found!",2000);          
   } 
   } 
} 
PDRequest.send(params); 
} 

Where PDJsonFeatures[i].attributes['amount'] values are 1 or 2 or 3 or..10 ResultZoomLoc is function for zooming to the location onclicking result.

Only the ELSE part of openlayers Filter is working here. Also the label "${getLabel}" is getting as undefined

Answer 1

You have a layer with amount as a field in attributes, passing the value will be as follow

var qty = 1000; //Example of value to be compare.

rules: [
    new OpenLayers.Rule({
        filter: new OpenLayers.Filter.Comparison({
        type: OpenLayers.Filter.Comparison.EQUAL_TO,
        property: "amount", 
        value: qty 
        }),
        symbolizer: {
        fillColor: '#34f2f9'
        }
    }),
    new OpenLayers.Rule({

        elseFilter: true,
        symbolizer: {
        fillColor: '#fff'
        }
    })
 ]

Full example:
http://dev.openlayers.org/examples/filter-strategy.html

JS code:
http://dev.openlayers.org/examples/filter-strategy.js

Answer 2

When inspecting the source of the Extended Clustering Example you can see that the property takes an attribute of the vector as input.

// creating the feature with an attribute "clazz"
var f = new OpenLayers.Feature.Vector(p, {clazz: clazz});

// defining the rule using the attribute "clazz" comparing with the value
new OpenLayers.Rule({
    filter: new OpenLayers.Filter.Comparison({
        type: OpenLayers.Filter.Comparison.LESS_THAN,
        property: "clazz",
        value: 4
    })
})