Question

I have an NSImageView subclass that I use for dragging and dropping Files onto in my app.

To do this I created a subclass of NSImageView and also dragged the NSImageView onto my XIB, I then set the class of the XIB NSImageView Object to my custom subclass.

Everything works well with the drag and drop and I know I have the correct file after the drag.

The problem comes in when I want to update a textfield on the MainViewController based on the file dragged in.

I created the following subclass and protocol

#import <Cocoa/Cocoa.h>
#import <Quartz/Quartz.h>

@protocol PDFDraggedIntoWell <NSObject>
@required
-(void)PDFDraggedIntoWellWithURL:(NSURL*) importedURL;

@end


@interface DragAndDropImageView : NSImageView

@property (strong) id <PDFDraggedIntoWell> delegate;

@end

Then in my implementation in the subclass I try to call the delegate method

-(void) finishedDragginInFileWithURL:(NSURL*) importedURL{
    if( self.delegate != nil && [ self.delegate respondsToSelector: @selector(PDFDraggedIntoWellWithURL:)]) {
        [self.delegate performSelector:@selector(PDFDraggedIntoWellWithURL:) withObject:importedURL];
    }
}

The problem I run into is how do you assign the delegate. From the XIB NSImageView to my MainviewController I connect up an IBOutlet

@property (weak) IBOutlet DragAndDropImageView *draggedFileImageView;

And I have declared that my ViewController will receive the delegate

@interface MyMainUIViewController ()<PDFDraggedIntoWell>

with the appropriate method implemented

-(void) PDFDraggedIntoWellWithURL:(NSURL *)importedURL{   }

Now I have tried in various places to assign delegate to self (in viewDidLoad – which doesn’t get called since the view is being loaded in a XIB??) and also in

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

but all I get back is the delegate is still nil when debugging.

What am I doing wrong? Thanks for the help!!

Answer 1

If you are using xibx the initWithCoder method is called for initialization. Set your delegate there.

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        UIView *myView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10, 10)];
        myView.delegate = self;
    }
    return self;
}

Alternatively set the delegate via interface builder by dragging wile holding ctrl from the File’s Owner to your view. Like this: