network_lib_part3.m

// NetworkRequest.h
typedef void(^NetworkRequestCompletionHandler)(NSData *data);

@interface NetworkRequest : NSObject

@property (nonatomic, strong, readonly) NSURL* url;

- (id)initWithURL:(NSURL*)url;
- (void)performWithCompletionHandler:(NetworkRequestCompletionHandler)completionHandler

@end

// NetworkRequest.m
#import "NetworkRequest.h"

@interface NetworkRequest ()

@property (nonatomic, strong, readwrite) NSURL *url;
@property (nonatomic, copy) NetworkRequestCompletionHandler completionHandler;
@property (nonatomic, strong) NetworkRequest *selfRef;
@property (nonatomic, strong) NSData *downloadedData;

@end

@implementation NetworkRequest

- (void)dealloc {
    NSLog(@"Hey!! NetworkRequest deallocated");
}

- (id)initWithURL:(NSURL*)url {
    if(self = [super init]) {
        _url = url;
    }
    return self;
}

- (void)performWithCompletionHandler:(NetworkRequestCompletionHandler)completionHandler {
    
    self.completionHandler = completionHandler;
//    self.selfRef = self;
    
      __weak NetworkRequest* weakSelf = self;
      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
          [weakSelf internal_requestCompleted];
      });
}

- (void)internal_requestCompleted {
    NSLog(@"Hey!! NetworkRequest completed");
    
    if(self.completionHandler) {
        self.completionHandler(self.downloadedData);
    }
    
    self.completionHandler = nil;
//    self.selfRef = nil;
}