[OpenLayers-Users] Problems with IE8 and GeoJSON

[Gerhard Dünnebeil]

Hi everybody.

Not sure this problem already got discussed, if yes.....please give me a 
pointer to it. Otherwise  .....



I try to display a vector layer using a fixed strategy and GeoJSON. 
Things work fine under Firefox.

When I test things with IE8, things fail. I run IE8 in default mode, no 
special headers or anything set on the web page that holds the map or 
elsewhere.

I digged deeper into it and found the following strange behaviour:
When the Layer is about to be drawn, data is fetched from the net and 
converted from JSON to java script. This happens in the read method 
(GEOjson.js/Line 64, see code excerpt below)

A bit below (line 69) the conversion is done into the variable "obj".
When you look at the "obj" variable at this point it holds an array 
named features *but* the feature array has *no* length property. 
Otherwise the array is correct with respect to the input data.

In line 108 this feature array is iterated with a reference to the 
length property. When IE8 interprets this statement the feature array 
suddenly *has* a length property but it is wrong (too big, 3 instead of 2).
As a follow-up error this causes the loop to break via the catch block 
when features[2] is accessed and gives back an empty result instead of 
the expected.

Is this a known problem?
How to work around it?

thanks for any help and
best regards
Gerhard

------------------------------------------
Appendix 1, the code mentioned above)

read: function(json, type, filter) {
        type = (type) ? type : "FeatureCollection";
        var results = null;
        var obj = null;
        if (typeof json == "string") {
line 69:            obj = OpenLayers.Format.JSON.prototype.read.apply(this,
                                                              [json, 
filter]);
        } else {
            obj = json;
        }   
        if(!obj) {
            OpenLayers.Console.error("Bad JSON: " + json);
        } else if(typeof(obj.type) != "string") {
            OpenLayers.Console.error("Bad GeoJSON - no type: " + json);
        } else if(this.isValidType(obj, type)) {
            switch(type) {
                case "Geometry":
                    try {
                        results = this.parseGeometry(obj);
                    } catch(err) {
                        OpenLayers.Console.error(err);
                    }
                    break;
                case "Feature":
                    try {
                        results = this.parseFeature(obj);
                        results.type = "Feature";
                    } catch(err) {
                        OpenLayers.Console.error(err);
                    }
                    break;
                case "FeatureCollection":
                    // for type FeatureCollection, we allow input to be 
any type
                    results = [];
                    switch(obj.type) {
                        case "Feature":
                            try {
                                results.push(this.parseFeature(obj));
                            } catch(err) {
                                results = null;
                                OpenLayers.Console.error(err);
                            }
                            break;
                        case "FeatureCollection":
line 108:                            for(var i=0, 
len=obj.features.length; i<len; ++i) {
                                try {
                                    
results.push(this.parseFeature(obj.features[i]));
                                } catch(err) {
                                    results = null;
                                    OpenLayers.Console.error(err);
                                }
                            }
                            break;
                        default:
                            try {
                                var geom = this.parseGeometry(obj);
                                results.push(new 
OpenLayers.Feature.Vector(geom));
                            } catch(err) {
                                results = null;
                                OpenLayers.Console.error(err);
                            }
                    }
                break;
            }
        }
        return results;
  
------------------------------------------------
Appendix 2, the JSON data

{ "type" : "FeatureCollection", "features" : [ { "type" : "Feature" 
,"geometry": { "type": "Point", "coordinates": [291068,270013] } 
,"properties": { "img_url": "icons/green_dot.gif" } }, { "type" : 
"Feature" ,"geometry": { "type": "Point", "coordinates": [291069,269967] 
} ,"properties": { "img_url": "icons/red_dot.gif" } }, ] }