[OpenLayers-Users] populate vector layer from json response

[Nicholas Efremov-Kendall]

Hi guys thanks for the previous advice,

I'm still running into an issue, and I'm not sure how to resolve it. When I
first use a OpenLayers.LonLat and transform the point, I get the lon
converted correctect, but the lat is returned NaN. If I don't transform it,
the coordinates remain correct.

tweet.point = new
OpenLayers.LonLat(tweet.geo.coordinates[0],tweet.geo.coordinates[1]).transform(new
OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());

I've been playing around with some different iterations, and I can get
tweet.point to alert out with ever tweet that's pulled into the plotting
function, but the markers aren't added. The issue seems to be with how I'm
calling the transform function, because somehow after calling the function I
get NaN's for the lat-lon's inside the point object. I'm really hitting a
wall here.



On Tue, Jun 21, 2011 at 3:23 AM, Nick Kendall <n.e.kendall at gmail.com> wrote:

> Thanks! Will take another crack at this Tom!
>
> Sent from my mobile device
>
> On Jun 21, 2011, at 2:37 AM, "Sveen Atle Frenvik (Geomatikk IKT)" <
> Atle.Frenvik.Sveen at geomatikk.no> wrote:
>
> try using an OpenLayers.Geometry.Point instead of an OpenLayers.LonLat
>
> ie (untested, but i think this is rather correct):
>
> function parseTweetsQ(){
>     if (tweetsQ.length > 0) {
>         var tweet = tweetsQ.pop();
>         if (tweet.geo){
>             tweet.point = new
> OpenLayers.Geometry.Point(tweet.geo.coordinates[0],tweet.geo.coordinates[1]).transform(new
> OpenLayers.Projection("EPSG:4326"),map.getProjectionObject());
>             tweet.attributes = {}; //in this you coukd stuff attributes of
> the tweet for easy access on clicks etc.
>              plotTwt(tweet);
>         }
>     }
> }
>
>  function plotTwt(tweet){
>     //why do you keep adding the layer for each tweet?
>      map.addLayer(tweetz);
>     tweet.marker = new
> OpenLayers.Feature.Vector(tweet.point,{attributes:{tweet.attributes]});
>     tweetz.addFeatures([tweet.marker]);
> }
>
>
>
> On 2011-06-21 05:00, Nicholas Efremov-Kendall wrote:
>
> Hi Phil et al,
>
>  Thanks for your response. The code as is does iterate through the
> features as they are returned. I have a handle on it up to the plotting
> function. An alert on the tweet.marker object returns [object Object], while
> tweet.latlng returns readable coordinates lon=38.6834,lat=-90.4313. I guess
> what I'm unsure about is how to parse the object which is passed to the
> third function. Thanks again.
>
>
>  function acquireTweets(){
> $.getJSON(createTWTsrcURL(), function(data){
> if(data.results)
> $.each(data.results, function(i, tweet){
> if (tweet.geo || tweet.location)
> tweetsQ.push(tweet);
> });
> refreshQuery = data.refresh_url;
> });}
>
>  function parseTweetsQ(){
> if (tweetsQ.length > 0) {
> var tweet = tweetsQ.pop();
> if (tweet.geo){
> tweet.latlng = new
> OpenLayers.LonLat(tweet.geo.coordinates[0],tweet.geo.coordinates[1]);
> plotTwt(tweet);
> }}}
>
>  function plotTwt(tweet){
>  map.addLayer(tweetz);
> tweet.marker = new OpenLayers.Feature.Vector(new
> OpenLayers.Geometry.Point(tweet.latlng).transform(new
> OpenLayers.Projection("EPSG:4326"),map.getProjectionObject()));
> tweetz.addFeatures([tweet.marker]);}
>
>
>
>
> On Mon, Jun 20, 2011 at 9:13 PM, Phil Scadden < <p.scadden at gns.cri.nz>
> p.scadden at gns.cri.nz> wrote:
>
>> I have no idea what the object returned by twitter is but surely, but if
>> you are using jsonp, then
>> have in your code something like:
>> jsonp_function(json)
>> where jsonp_function is the name of jsonp callback and json is the
>> returned object. I would guess it contains an array of feature type
>> objects, so you would iterate through the array, creating feature for
>> each row, and calling vectorLayer.addFeatures(features) to add them to
>> the vector layer.
>>
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>
> --
> Atle Frenvik Sveen
> Utvikler
> Geomatikk IKT AS
> tlf: 45 27 86 89 <atle.frenvik.sveen at geomatikk.no>atle.frenvik.sveen at geomatikk.no
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