Value transfer issue

Question

Is there any explanation why the NSLog always displays null when running this code?

ExtratoDeNotasSideMenuViewController *extratoDeNotasSideMenuViewController =   [[ExtratoDeNotasSideMenuViewController alloc] init];
extratoDeNotasSideMenuViewController.userImageView.image = [UIImage imageNamed:@"Icone_SideBar.png"];
NSLog(@"%@", extratoDeNotasSideMenuViewController.userImageView.image);

2014-10-28 13:40:50.594 E-proinfo[913:51418] (null)

By "returns" you mean "displays"? If `NSLog()` displays "null" it is because `extratoDeNotasSideMenuViewController.userImageView.image` is `null`. So perhaps the question should be "Why does `extratoDeNotasSideMenuViewController.userImageView.image` return `null`?" — zaph, Oct 28 '14 at 15:57

Ian MacDonald · Accepted Answer · 2014-10-28T16:15:53.103

Potential causes:

Your ExtratoDeNotasSideMenuViewController init returned nil because there was an error during initialization.
```
NSLog(@"%@", extratoDeNotasSideMenuViewController); // Does this display '(null)'?
```
Your userImageView isn't initialized yet because you don't initialize it in ExtratoDeNotasSideMenuViewController init.
```
NSLog(@"%@", extratoDeNotasSideMenuViewController.userImageView); // Does this display '(null)'?
```
Your image is nil because you don't have an image named Icone_SideBar.png.

You should either add NSLog statements or add a breakpoint and use po to inspect your objects.

Edit: If you want to set something on your view controller before your view is created (or as a persistent thing between view creations if you expect your view controller to destroy its view and then recreate it at some point), you should use a property.

Consider the following:

@interface ExtratoDeNotasSideMenuViewController
@property (strong) UIImage *myUserImage;
...
@end

@implementation ExtratoDeNotasSideMenuViewController
...
- (void)loadView {
  [super loadView];
  ...
  [self.userImageView setImage:self.myUserImage];
  ...
}
...
@end

...
  ExtratoDeNotasSideMenuViewController *extratoDeNotasSideMenuViewController =   [[ExtratoDeNotasSideMenuViewController alloc] init];
  extratoDeNotasSideMenuViewController.myUserImage = [UIImage imageNamed:@"Icone_SideBar.png"];

When running NSLog(@"%@", extratoDeNotasSideMenuViewController); 2014-10-28 14:08:18.015 E-proinfo[1026:194071] was displayed When running NSLog(@"%@", extratoDeNotasSideMenuViewController.userImageView); 2014-10-28 14:08:18.015 E-proinfo[1026:194071] (null) Was displayed — Douglas Pfeifer, Oct 28 '14 at 16:09
So then the second bullet applies... Your `userImageView` is `nil` because you aren't initializing it in your view controller's `init`. You're probably initializing it in your `viewDidLoad` or `loadView`, neither of which will have been called yet. — Ian MacDonald, Oct 28 '14 at 16:12

Value transfer issue

1 Answers1