iOS - Parse: findObjectsInBackgroundWithBlock with completion - ios

Question

I'm fetching data using findObjectsInBackgroundWithBlock but I have to use the data when all of it is gathered. I don't know how to implement a callback or anything which would alert me once all the data is retrieved and ready for me to use. Is there any way to get alerted?
Code:
[query findObjectsInBackgroundWithBlock:^(NSArray* array, NSError* error)
{
if(!error)
{
if([array count] > 0)
{
PFObject* relationship = [array objectAtIndex:0];
if([relationship.objectId length] > 0)
{
if([[relationship objectForKey:#"initiatedBy"] isEqualToString:parseID]) // relationship initiated by current user -youLike
{
[youLike addObject:relationship];
NSLog(#"youLike added");
}
else
{
[likeYou addObject:relationship];
NSLog(#"likeYou added");
}
}
else NSLog(#"Custom error when cycling through user relationships: objectId is nil");
}
else
{
NSLog(#"Custom error when cycling through user relationships: Relationship at index %d could not be found in database", i);
}
}
else
{
NSLog(#"Error when cycling through user relationships: %#", error);
}
}

Answer 1

You need to use Blocks
Declare the Block (Here you choose your block types)
typedef void (^YourBlock)(NSArray *array, NSError *error);
Add the block and the findObjectsInBackgroundWithBlock in a method.
- (void) yourMethod:(YourBlock)block {
[query findObjectsInBackgroundWithBlock:^(NSArray *array, NSError *error) {
//Do your things here if you want change something.
//For instance: convert types, convert errors.
block(array, error); //Is called when every thing is retrieve.
}
}
Call your method in the Application
SomeClass *someClass = [SomeClass alloc]init];
[[object getScoresFromParse:^(NSArray *array, NSError *error) {
//Everything complete here.
}];

Answer 2

You can use blocks.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
[query findObjectsInBackgroundWithBlock:^(NSArray* array, NSError* error)
{
if(!error)
{
if([array count] > 0)
{
PFObject* relationship = [array objectAtIndex:0];
if([relationship.objectId length] > 0)
{
// It will be called when Parse finishes.
dispatch_async(dispatch_get_main_queue(), ^{
if([[relationship objectForKey:#"initiatedBy"] isEqualToString:parseID]) // relationship initiated by current user -youLike
{
[youLike addObject:relationship];
NSLog(#"youLike added");
}
else
{
[likeYou addObject:relationship];
NSLog(#"likeYou added");
}
// [...yourcode...]
});
}
else {
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"Custom error when cycling through user relationships: objectId is nil");
});
}
}
}
}];
}];