CODEWITHSUNDEEP
iosobjective-cuiviewcontroller
rockhard
rockhard

Reputation: 349

Can't get passed data in viewDidLoad method

I'm trying to pass some data to my view controller class like this:

MyViewController *vc = [[MyViewController alloc] init];
vc.myProperty = dataToBePassed;
[self.navigationController pushViewController:vc animated:YES];

I need to make some view configuring in viewDidLoad, but it seems that viewDidload called earlier than property assignment.

Then in MyViewController implementation:

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"%@", self.myProperty); // Here i get myProperty = nil
}

- (void)viewWillAppear
{
    [super viewWillAppear];
    NSLog(@"%@", self.myProperty); // Here i get myProperty = dataToBePassed but it's to late
}

How can i get passed data in viewDidLoad method without implementing singleton or delegate patterns?

Upvotes: 0

Views: 121

Answers (3)

jp2g
jp2g

Reputation: 692

While the code sample you provide looks technically correct, I'm with @john-elemans in that you need to show more code.

There is something that is referencing the view which causes it to load and therefore causes viewDidLoad to fire prematurely.

In any case, if something (such as your property) is absolutely essential to the correct building of your view structure, I'd put in its own designated initializer, e.g.,

- (id)initWithPhotoDiameter:(CGFloat)diameter
{
    self = [super init...]; // some VC initializer that you should call
    if (self) {
        _photoDiameter = diameter;
    }

    return self;
}

Notice the use of the backing instance variable _photoDiameter instead of self.photoDiameter. This is about the only place in a class where you should use the backing ivar, since self is still in the process of being initialized.

Upvotes: 0

A Salcedo
A Salcedo

Reputation: 6478

Technically there are two approaches that are quite common for lifecycle handling of view controllers related to an application.

Using XIBs When using XIBs one of the most common if not the most common process to create and setup your view controllers is done programmatically. Following this process, when you initialise the view controller you have the option of either overriding your init method in order for your view controller to have the information prior to loading the view and easing up the process of adjusting drawn content. You can also create a method within your view controller to be called in which you pass the data to be used by the view controller.

Using Storyboard If you are using storyboards I recommend that you trust segues setup through it. I have found that they make life easier and it will allow you to use certain methods to handle the transition. One of those is prepareForSegue:sender: Within that method I have found that it is easier to setup a view controller after it's initialized accessing the destination controller. You also might consider having all data there before viewDidLoad hence following the segue approach.

Upvotes: 0

Saheb Roy
Saheb Roy

Reputation: 5967

Try doing this

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:
                            @"MainStoryboard" bundle:[NSBundle mainBundle]];

MyViewController *vc = [storyboard  instantiateViewControllerWithIdentifier:@"storyboardIdentifier"];
vc.myProperty = dataToBePassed;
[self.navigationController pushViewController:vc animated:YES];

You have to set a storyboard identifier first in the storyboard for the view controller.

Upvotes: 1

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