How can a queryTask be executed synchronously? I'd like a feature set to be returned instead of deferred object.
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I use queryTask.execute in a cycle because I search all features from several layers that are found inside some rectangle.So I run by layers and for each layer call queryTask.execute and in callback function in its parameter "results" I get some feature set. Because this object does not contain corresponding layer id I'd like to create a new object that contains layer id and feature set. So I need callback function work synchronously. I tried your advice but this does not help: firstly the cycle is ended and only after that the callback or onComplete or .then of deferred begin to work (also in– user32439Commented Jun 15, 2014 at 13:44
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1 Answer
In instances like this, the API returns deferred objects in case you're interested in identifying when more than one request to a server has resolved, but its not something your application logic has to worry about if you're just dealing with one task at a time.
for example, when you call QueryTask.execute() and leverage the in-built callback, you can get a reference to the featureset output you want:
queryTask.execute(query, myCallback, myErrorBack);
...
myCallback(results) {
//do something
}
To work with QueryTask deferreds, you have an additional option to do something like this:
var myDeferred = queryTask.execute(query);
myDeferred.then(...
answered May 12, 2014 at 21:47
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Thanks, that makes sense however, I need to create a function/(web service?) that returns a feature set. The callback function performs a task, but I need to return a result, not a promise. How would you go about that?– MatejCommented May 13, 2014 at 21:00
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Let me try to rephrase.. If I return a result of a queryTask, I get a promise. Let's say I have a function called myFunction that performs a queryTask based on a polygon geometry. The function call would look something like: var result = myFunction(myGeometry, myMapServiceUrl); Since the function returns before the queryTask completes, the result is of promise type. Perhaps, I need to treat the result as it was an actual featureSet?– MatejCommented May 14, 2014 at 18:44