I want to show users current location in map and I know it's not instantaneous task. I want to call my showCurrentLocation() function in the ASYNC task. I was trying to learn call back closures but i could not understand how can I create ASYNC task for this. I know this is not a best question template for stackoverflow but I don't know how can I ask differently. Thank you for any help. Have a nice coding.
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1have a look at NSOperation nshipster.com/nsoperationmgratzer– mgratzer2015-08-24 11:22:24 +00:00Commented Aug 24, 2015 at 11:22
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Thank you. I will look the NSOperationemresancaktar– emresancaktar2015-08-24 11:30:31 +00:00Commented Aug 24, 2015 at 11:30
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2 Answers
In the past I've made a class called AsyncTask for usage purposes like the one you described here.
Lately I've updated it for swift 3
It has 2 generic types:
BGParam - the type of the parameter sent to the task upon execution.
BGResult - the type of the result of the background computation.
If one of them(or both) isn't needed you can set it to Optional or just ignore.
In code example I refer the functions showCurrentLocation() & getCurrentLocation() that you mentioned in OP & comments.
BGParam is set to Int & BGResults is set to CLLocationCoordinate2D
AsyncTask(backgroundTask: {(param:Int)->CLLocationCoordinate2D in
print(param);//prints the Int value passed from .execute(1)
return self.getCurrentLocation();//the function you mentioned in comment
}, afterTask: {(coords)in
//use latitude & longitude at UI-Main thread
print("latitude: \(coords.latitude)");
print("latitude: \(coords.longitude)");
self.showCurrentLocation(coords);//function you mentioned in OP
}).execute(1);//pass Int value 1 to backgroundTask
Comments
There is a technology called GCD (Grand Central Dispatch) which you can use to perform such tasks.
let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
dispatch_async(dispatch_get_global_queue(priority, 0)) {
// do some task
dispatch_async(dispatch_get_main_queue()) {
// update some UI
}
}
2 Comments
emresancaktar
First of all thank you for your answer. I know the GCD. I wonder, Can I create custom async task with closure ? Think about this situation. Lets assume we have a getCurrentLocation() function and it returns us userCurrentLocation.latitude and longitude. I can't get values instantaneously so I have to use callback mechanism. It should tell me we found locations and there are the results so I can use them in main thread. If you put the getCurrentLocation function in the background thread. Does it solve my problem ? Will it work like a callback mechanism ? Thank you !
user3441734
using the global queue is not the best idea ... you newer know who use it. creating own concurrent queue is a little bit better solution here.
