Question

I am doing JSON parsing in my App, When I Use responseData = [NSMutableData data]; it crashes on [responseData setLength:0];

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

   [responseData setLength:0];   // CRASH HERE

}

and when I use responseData=[[NSMutableData alloc]init]; my program works fine. I already make property in .h file

@property (strong, nonatomic) NSMutableData* responseData;

and synthesize in .m file

@synthesize responseData;

Question : what is difference between [NSMutableData data] and [[NSMutableData alloc]init];

thanks

Answer 1

[NSMutableData data] returns an autoreleased object whereas [[NSMutableData alloc] init] returns a retained object.