How to create a simple NSURLRequest Callback? - ios

Question

I have created a class that will collect data from url data asynchronously, however my understanding of callbacks or whatever is not clear and I'm trying to find a simple way to reuse my class by having the calling method wait for data to be returned or set within the ApiManager class. I just need something to wakeup in another class when that process has been completed. Some processes have single request and others have multiple, why you will notice that I'm using [connection description] within the ApiManager class.
ApiManager.h
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#interface ApiManager : NSObject<NSURLConnectionDelegate>
{
NSMutableDictionary *_dataDictionary;
}
- (void)urlRequest:(NSURLRequest *)url;
#property (strong, nonatomic) NSMutableArray *results;
#end
ApiManager.m
#import "ApiManager.h"
#implementation ApiManager
- (void)urlRequest:(NSURLRequest *)url {
[[NSURLConnection alloc] initWithRequest:url delegate:self];
}
// basic connection classes
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
NSMutableData *responceOjb = _dataDictionary[ [connection description] ];
[_dataDictionary setObject:responceOjb forKey:[connection description]];
}
// append any data we find
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSMutableData *responceOjb = _dataDictionary[ [connection description] ];
[responceOjb appendData: data];
[_dataDictionary setObject:responceOjb forKey:[connection description]];
}
// --
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection
willCacheResponse:(NSCachedURLResponse*)cachedResponse {
// Return nil to indicate not necessary to store a cached response for this connection
return nil;
}
// wrap up and close the connect, move objects over to results or something
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[_results addObject:[connection description]];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
// The request has failed for some reason!
// Check the error var
NSLog(#"%#",error);
}
#end
The main View Controller test:
#import "ViewController.h"
#import "ApiManager.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self DoThisTest];
}
-(void)DoThisTest {
ApiManager *api = [[ApiManager alloc] init];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#",#"http://google.com"]]];
[api urlRequest:request];
if([api results]) {
NSLog(#"GOT DATA");
}
}

Answer 1

Well, there are a few options. You could add a block property onto your ApiManager class:
#property (copy, nonatomic) void (^doneHandler)();
And then invoke that block like so:
self.doneHandler();
You would invoke the block when you deem it appropriate (say, in your connectionDidFinishLoading: method).
With this approach, the definition of the block (callback) would happen in your view controller and look something like:
ApiManager *apiManager = [[ApiManager alloc] init];
apiManager.doneHandler = ^{
// Do whatever you need to do here.
};
Alternatively, you could add a method to your ApiManager with a signature like this:
- (void)sendRequestWithURL:(NSURL*)url completion:(void(^)())completion;
And use NSURLConnection's (or, better, NSURLSession's) block-based APIs. Those APIs have callbacks built in and you would simply invoke completion(); inside of the completion block of -[NSURLSession sendAsynchronousRequest:completion:].
Finally, you could define an ApiManagerDelegate protocol.
- (void)apiManagerDidFinishReceivingData:(ApiManager*)sender;
And add a delegate property to your ApiManager class.
#property (weak, nonatomic) id<ApiManagerDelegate>delegate;
Assign the delegate of your ApiManager in your ViewController:
ApiManager *apiManager = [[ApiManager alloc] init];
apiManager.delegate = self;
Call the delegate method inside of your implementation of NSURLConnectionDelegate's callbacks in ApiManager like so:
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[_results addObject:[connection description]];
[self.delegate apiManagerDidFinishReceivingData:self];
}
And implement the delegate method in ViewController:
- (void)apiManagerDidFinishReceivingData:(ApiManager*)sender {
// Do what you want to.
}
As an addendum, there are networking libraries available that do a lot of the heavy lifting and busy-work for you, most notably AFNetworking, if you're just trying to get stuff done. And, even if this is more of an academic exercise where you're trying to understand the patterns, looking at AFNetworking's APIs and implementation (it's open source) would be highly instructive.
Cheers