sendAsynchronousRequest method will excute block code before block outside code - ios

Question

when i use sendAsynchronousRequest method at that time this method inner block will execute after outside code will execute?
__block NSDictionary *dict;
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError)
{
NSInteger httpStatus = [((NSHTTPURLResponse *)response) statusCode];
NSLog(#"httpStatus inside block:%d",httpStatus);
if ([data length]>0 && connectionError==nil)
{
dict=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers|NSJSONReadingAllowFragments error:nil];
}
else if (connectionError)
{
UIAlertView *alt=[[UIAlertView alloc] initWithTitle:#"Error" message:[connectionError localizedDescription] delegate:self cancelButtonTitle:#"Ok" otherButtonTitles:nil, nil];
[alt show];
}
}];
return dict;//it will return null because it will run before execute inner block of sendAsynchronousRequest

Answer 1

Asynchronous request always run in the network thread.
Your [NSOperationQueue mainQueue] means that the block-callback will schedule in mainQueue.
If you wanna to wait until the request finished, you can use synchronous request, or use semaphore to block current thread.
See
+ (NSData *)sendSynchronousRequest:(NSURLRequest *)request returningResponse:(NSURLResponse **)response error:(NSError **)error;
but attention that this way to request will block current thread. be careful when using this way.

Answer 2

You should use block method
First define a block
typedef void (^OnComplate) (NSDictionary * dict);
- (void)viewDidLoad{
[self getDataWithBlokc:^(NSDictionary *dict) {
NSLog(#"%#",dict);
}];
}
Use the following method
-(void)getDataWithBlokc:(OnComplate)block{
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError)
{
NSInteger httpStatus = [((NSHTTPURLResponse *)response) statusCode];
NSLog(#"httpStatus inside block:%d",httpStatus);
if ([data length]>0 && connectionError==nil)
{
NSDictionary* dict=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers|NSJSONReadingAllowFragments error:nil];
block(dict);
}
else if (connectionError)
{
UIAlertView *alt=[[UIAlertView alloc] initWithTitle:#"Error" message:[connectionError localizedDescription] delegate:self cancelButtonTitle:#"Ok" otherButtonTitles:nil, nil];
[alt show];
}
}];
}