The UILabel is nil - ios

Question

I have a ContentPageViewController class, it has the IBOutlet stuff. I write my getter of ContentPageViewController in the ViewController like the following code.
ContentPageViewController.h
#interface ContentPageViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *busName;
#property (weak, nonatomic) IBOutlet UILabel *busTime;
#property (weak, nonatomic) IBOutlet UILabel *busType;
#end
ViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
// instantiation from a storyboard
ContentPageViewController *page = [self.storyboard instantiateViewControllerWithIdentifier:#"ContentPageViewController"];
self.page = page;
// send url request
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:#"https://api.apb-shuttle.info/now" ]];
[self sendURLRequest:request];
// add the view of ContendPageViewController into ViewController
[self.view addSubview:self.page.view];
}
// It works if i remove the following code
- (ContentPageVC *)page
{
if (_page) _page = [[ContentPageViewController alloc] init];
return _page;
}
Nothing happened when I updated it. And it gave me a nil.
- (void)updateUI
{
// I got null here
NSLog("%#", self.page.busName)
// The spacing style font
NSDictionary *titleAttributes = #{
NSKernAttributeName: #10.0f
};
NSDictionary *attributes = #{
NSKernAttributeName: #5.0f
};
self.page.busName.attributedText = [[NSMutableAttributedString alloc] initWithString:bus.name
attributes:titleAttributes];
self.page.busTime.attributedText = [[NSMutableAttributedString alloc] initWithString:bus.depart
attributes:titleAttributes];
self.page.busType.attributedText = [[NSMutableAttributedString alloc] initWithString:bus.note
attributes:attributes];
}
The following code is when I called the updateUI:
- (void)sendURLRequest:(NSURLRequest *)requestObj
{
isLoading = YES;
[RequestHandler PerformRequestHandler:requestObj withCompletionHandler:^(NSDictionary *data, NSError *error) {
if (!error) {
bus = [JSONParser JSON2Bus:data];
// Add the bus object into the array.
[self.busArray addObject: bus];
[[NSOperationQueue mainQueue] addOperationWithBlock: ^{
[self updateUI];
isLoading = NO;
}];
} else {
NSLog(#"%#", [error localizedDescription]);
}
}];
}
But it worked if I removed the getter above.
I have no idea how it works, please give me some hint. Thanks.

Answer 1

Check your IBOutlet is connected.
Check the method you are calling isn't called before the view is created from the storyboard/nib
EDIT
The lines of code that you added, are overriding your getter. And every time you call self.page, your creating a new instance!
// It works if i remove the following code
- (ContentPageVC *)page
{
if (_page) _page = [[ContentPageViewController alloc] init];
return _page;
}
It should be like so:
// It works if i remove the following code
- (ContentPageVC *)page
{
if (!_page) _page = [[ContentPageViewController alloc] init]; // Added the ! mark, only if nil you would create a new instance.
return _page;
}
Plus you are calling alloc init on it, so Its not the same instance from storyboard!
So you should do this:
- (ContentPageVC *)page
{
if (!_page) _page = [self.storyboard instantiateViewControllerWithIdentifier:#"ContentPageViewController"];
return _page;
}
And remove this lines of code:
// instantiation from a storyboard
ContentPageViewController *page = [self.storyboard instantiateViewControllerWithIdentifier:#"ContentPageViewController"];
self.page = page;
Every time you call "self.page" the override getter function will call. and return the same instance.