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iOS Displaying API Data with Collection Views in Objective-C Show Me the Data - API’s, OAuth, and NSURLSession Populating the CollectionView

Evan Goodwin
PLUS
Evan Goodwin
Courses Plus Student 22,260 Points
Posted by Evan Goodwin
Evan Goodwin
Courses Plus Student 22,260 Points

Repeated pictures of like places, but can't see difference in code.

I have pasted in the ProjectFile version of refreshFoursquare and everything works. My own code leads to repeated photos. I have checked the code difference and the only difference was a misspelling in the ProjectFile version(which works) - requst instead of request (NSURLRequest *requst = [[NSURLRequest alloc]initWithURL:url];) .

Here is the code.

Working Project File: 

-(void)refreshFoursquare{
    NSURLSession *session = [NSURLSession sharedSession];
    NSString *urlString = [[NSString alloc]initWithFormat:@"https://api.foursquare.com/v2/users/self/venuelikes/?oauth_token=%@&v=%@&m=%@", self.accessToken, DATA_VERSION_DATE, DATA_FORMAT];
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [[NSURLRequest alloc]initWithURL:url];
    NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSData *data = [[NSData alloc]initWithContentsOfURL:location];

        NSDictionary *responseDict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
        self.likedArray = [responseDict valueForKeyPath:@"response.venues.items.id"];

        self.venueArray = [[NSMutableArray alloc]init];

        for(NSString *venueID in self.likedArray){
            NSString *urlStringVenue = [[NSString alloc]initWithFormat:@"https://api.foursquare.com/v2/venues/%@?oauth_token=%@&v=%@&m=%@", venueID, self.accessToken, DATA_VERSION_DATE, DATA_FORMAT];
            NSURL *urlVenue = [NSURL URLWithString:urlStringVenue];
            NSURLRequest *requestVenue = [[NSURLRequest alloc]initWithURL:urlVenue];
            NSURLSessionDownloadTask *taskVenue = [session downloadTaskWithRequest:requestVenue completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
                NSData *dataVenue = [[NSData alloc]initWithContentsOfURL:location];
                NSDictionary *responseDictVenue = [NSJSONSerialization JSONObjectWithData:dataVenue options:kNilOptions error:nil];
                [self.venueArray addObject:responseDictVenue];
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.collectionView reloadData];
                });
            }];
            [taskVenue resume];
        }


    }];

    [task resume];
}

MIne Code with Repeating Pictures. 

-(void)refreshFoursquare{
    NSURLSession *session = [NSURLSession sharedSession];
    NSString *urlString = [[NSString alloc]initWithFormat:@"https://api.foursquare.com/v2/users/self/venuelikes/?oauth_token=%@&v=%@&m=%@", self.accessToken, DATA_VERSION_DATE, DATA_FORMAT];
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [[NSURLRequest alloc]initWithURL:url];
    NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSData *data = [[NSData alloc]initWithContentsOfURL:location];

        NSDictionary *responseDict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
        self.likedArray = [responseDict valueForKeyPath:@"response.venues.items.id"];

        self.venueArray = [[NSMutableArray alloc]init];

        for(NSString *venueID in self.likedArray){
            NSString *urlStringVenue = [[NSString alloc]initWithFormat:@"https://api.foursquare.com/v2/venues/%@?oauth_token=%@&v=%@&m=%@", venueID, self.accessToken, DATA_VERSION_DATE, DATA_FORMAT];
            NSURL *urlVenue = [NSURL URLWithString:urlStringVenue];
            NSURLRequest *requestVenue = [[NSURLRequest alloc]initWithURL:urlVenue];
            NSURLSessionDownloadTask *taskVenue = [session downloadTaskWithRequest:requestVenue completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
                NSData *dataVenue = [[NSData alloc]initWithContentsOfURL:location];
                NSDictionary *responseDictVenue = [NSJSONSerialization JSONObjectWithData:dataVenue options:kNilOptions error:nil];
                [self.venueArray addObject:responseDictVenue];
                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.collectionView reloadData];
                });
            }];
            [taskVenue resume];
        }


    }];

    [task resume];
}