Example of iAsync library usage to wrap data acquisition. ( library link : https://github.com/EmbeddedSources/iAsync/ )

iAsyncDownloadExample.mm

-(void)clientCode
{
    JFFAsyncOperation dataLoader_ = [ builder buildDataLoaderWithAuthentication ];
    dataLoader_( nil, nil, ^void( id result, NSError* error )
    {
        // your data is ready. Show it to the user
    } );
}


// ==============
-(JFFAsyncOperation)buildDataLoaderWithAuthentication
{
    return sequenceOfAsyncOperations( [ self asyncAuthentication ], [ self buildDataLoader ], nil );
}



-(JFFAsyncOperation)buildDataLoader
{
  //// some initialization code
	
    JFFSyncOperation syncDbFetch_ = ^id( NSError** errorPtr_ )
    {
        return [ database_ doSomeQuery: someQueryData_
								 error: errorPtr_ ];
    };
	JFFAsyncOperation asyncDbFetch_ = asyncOperationWithSyncOperation( syncDbFetch_ )
	
	
	JFFAsyncOperationBinder dbImport_ = ^JFFAsyncOperation( id dataToImport )
	{
	    JFFSyncOperation syncDbImport_ = ^id( NSError** errorPtr_ )
	    {
	        if ( [ database_ importData: dataToImport
							 error: errorPtr_ ] )
			{
				return [ NSNull null ];
			}
			
			return nil;
	    };
		
		return asyncOperationWithSyncOperation( syncDbImport_ )
	}

	
    JFFURLConnectionParams* params_ = [ JFFURLConnectionParams new ];
    params_.url               = url_;
	// more download params setup
	JFFAsyncOperation download_ = dataURLResponseLoader( params_ );
	

	JFFAsyncOperation downloadAndImport_ = bindSequenceOfAsyncOperations( download_, dbImport_, nil );
	JFFAsyncOperation dataFromInet_ = sequenceOfAsyncOperationsArray( @[downloadAndImport_, asyncDbFetch_ ] );
	
	JFFAsyncOperation tryCacheFirst = trySequenceOfAsyncOperations( asyncDbFetch_, dataFromInet_, nil );

	return tryCacheFirst;
}