IBOutlet is nil inside custom UIView (Using STORYBOARD)

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忘掉有多难
忘掉有多难 2020-12-25 13:22

I have a custom UIView class. Inside it I have declared an IBOutlet property for UIImageView.

#import 

        
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7条回答
  • 2020-12-25 13:45

    Can you not use the setter for properties, that way you can do what you need when it's actually populated?

    @IBOutlet weak var xxx:UIKitClass! {
      didSet { 
        outletSetup() 
      }
    }
    
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  • 2020-12-25 13:47

    Override awakeFromNib in your view - this is the first lifecycle method to be called after the IBOutlets have been assigned and is the right place for your code.

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  • 2020-12-25 13:47

    in your .h file you need to replace your code:

    #import <UIKit/UIKit.h>
    
    @interface SettingItem : UIView{
    
    }
    
    @property (strong, nonatomic) IBOutlet UIImageView *myImage;
    
    @end
    

    With this code

    #import <UIKit/UIKit.h>
    
    @interface SettingItem : UIView{
    
      IBOutlet UIImageView*myImage;
    
    }
    
    @end
    

    You are not actually telling Xcode what myImage is, you are just making it a strong, nonatomic property

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  • 2020-12-25 14:02

    I just had the exact same problem and the solution is really easy:

    You're accessing myImage to soon - that's it.

    Withing -(id) initWithCoder:(NSCoder *)aDecoder{ and - (id)initWithFrame:(CGRect)frame the UIView is not already drawed. So myImage is not initalized yet.

    You can test it if you add a UIButton and an IBAction and do something like this:

    - (IBAction)buttonClicked:(id)sender {
        NSLog(@"%@",myImage);
    }
    

    And you'll see how myImage is not nil anymore.

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  • 2020-12-25 14:02

    I had similar problems, but I finally figured out what was wrong - It was a difference in the idiom between XIB files and Storyboards.

    In all the tutorials that I had seen with Xib files, if I had a UITableViewController create a DetailViewController to let me edit the content of the items in the table, then the tableViewController created an instance of the DVC once when it first revealed it, but then reused that same DVC instance whenever it needed to edit another item on the list.

    With storyboards, it appears that the a view that is revealed by a table view is typically created new each time the table view calls it up (and it doesn't call up the version of init that is in the UIViewController template). As a previous answer stated, you have to wait until "ViewDidLoad" to access any of the controls, even if you have shown this view before.

    I hope this helps.

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  • 2020-12-25 14:03

    Call [self baseInit] inside -(void)viewWillAppear:(BOOL)animated. myImage should have a value there.

    #import "SettingItem.h"
    
    @implementation SettingItem
    
    - (id)initWithFrame:(CGRect)frame
    {
        self = [super initWithFrame:frame];
        if (self) {
            // Initialization code
    
        }
        return self;
    }
    
    -(id) initWithCoder:(NSCoder *)aDecoder{
        self = [super initWithCoder:aDecoder];
        if (self) {
            // Initialization code
    
        }
        return self;
    }
    -(void)viewWillAppear:(BOOL)animated
    {
       [self baseInit];
    }
    
    - (void) baseInit{
        NSLog(@"myImage %@"self.myImage);
    }
    
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