iOS NSError/NSDictionary for callbacks - ios

Question

I am developing a framework which requires error callbacks. I have used delegate methods to give error callbacks to the users(developer) of the framework. Can I use NSError to indicate error details in the delegate method or simply use NSDictionary instead ? Are there any memory issues concerned here?

Answer 1

Instead of delegate methods, you should use blocks with proper error handling, something like this:
Interface:
typedef void(^ResultBlock)(id result, NSError *error);
extern NSString * const DummyErrorDomain;
enum{
DummyErrorReason1,
DummyErrorReason2
};
#interface Dummy : NSObject
-(void)doSomething:(ResultBlock)resultBlock;
#end
Implementation with async NSURLConnection:
NSString * const DummyErrorDomain = #"DummyErrorDomain";
#interface Dummy ()
#property (strong) ResultBlock resultBlock;
#property NSURLConnection *connection;
#property NSMutableData *responseData;
#end
#implementation Dummy
-(void)doSomething:(ResultBlock)resultBlock
{
self.resultBlock = resultBlock;
self.responseData = [[NSMutableData alloc] init];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:#"dummyURL"]];
self.connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
self.resultBlock(nil,error);
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
self.resultBlock(self.responseData, nil);
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
[self.responseData appendData:data];
}
#end
Usage:
-(void)usage
{
Dummy *dummy = [[Dummy alloc] init];
[dummy doSomething:^(id result, NSError *error) {
if(result){
// everything went fine
}else{
// error handling
}
}];
}