How to Replace Values Between View Controllers? - ios

Question

I'm building an iOS app that parses JSON data when the first ViewController loads. In another ViewController, I have a UIPicker, which includes an array objects that pass their own corresponding urls, and a UIButton which calls the segue back to the first ViewController. However, when I call the segue, the View Controller still parses the same data from the initial nsurl, instead of the data called to replace it. How do I fix this so that when I select an object from the UIPicker and pass the data to the next controller, the first view controller parses that data accordingly?
Here is my code:
MainVC.m
-(void)viewDidLoad{
[super viewDidLoad];
_bburl = [NSURL URLWithString:#"http://www.example.com/api/sites?count=75"];
NSData *jsonData = [NSData dataWithContentsOfURL:_bburl];
NSURLSession *session = [NSURLSession sharedSession];
NSURLRequest *request = [[NSURLRequest alloc]initWithURL:_bburl];
NSURLSessionDownloadTask *task = [session downloadTaskWithURL:_bburl completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error){
NSLog(#"%#", response);
NSData *data = [[NSData alloc]initWithContentsOfURL:location];
NSDictionary *dataDictionary = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
. . . . .
}
MenuVC.m
-(void)viewDidLoad{
[super viewDidLoad];
self->catArray = [[NSArray alloc] initWithObjects:#"All",#"4-Letter", #"Animal", #"Auction", #"Blog", #"Business", #"Celluar", #"Children",#"Community", #"Consulting", #"Dating", #"Design", #"Download", nil];
self->URLArray = [[NSMutableArray alloc]init];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=4-letter"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=animal"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=auction"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=blog"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=business"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=cellular"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=children"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=community"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=consulting"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=dating"];
[URLArray addObject: #"https://www.exapmle.com/api/sites/?count=75&category=design"];
[URLArray addObject: #"https://www.example.com/api/sites/?count=75&category=download"];
self->picker = catArray;
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
// This method returns the number of components we want in our Picker.
// The components are the colums.
return 1;
}
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
// This returns the number of rows in each component. We use the count of our array to determine the number of rows.
return [self->catArray count];
return 0;
}
#pragma mark Picker Delegate Methods
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
return [self->catArray objectAtIndex:row];
return 0;
}
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
selectedRow = [pickerView selectedRowInComponent:0];
NSString *catURLString = [URLArray objectAtIndex:selectedRow];
catURL = [NSURL URLWithString:catURLString];
MainViewController *mainVC = [[MainViewController alloc]init];
mainVC.bburl = catURL;
NSLog(#"%d, %#", selectedRow, catURL);
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:#"backFromMenuSegue"]) {
NSString *catURLString = [URLArray objectAtIndex:[self->picker selectedRowInComponent:0]];
catURL = [NSURL URLWithString:catURLString];
MainViewController *mainVC = segue.destinationViewController;
mainVC.bburl = catURL;
NSLog(#"Selected url: %#",catURL);
}
}

Answer 1

When you call the segue back to the first ViewController the first viewController has already loaded. So method viewDidLoad will not be called. The quickest and dirty way to solve this is move all the code in viewDidLoad to viewWillAppear