Drag and drop just to extract file path

Question

I'm writing a Cocoa GUI app to facilitate working with a command-line program. The scenario is quite similar to what I see in the Apple FileMerge.app. I'd have a NSView (or a drop pocket of whichever class appropriate) into which I can drag the file icons just in order to retrieve file's path, one by one, no visualization, no checking for file types, just for assembling a list of files to eventually be passed to the data crunching program as command line arguments. I've come across CocoaDragAndDrop sample program, which does great work in displaying dragged picture tiff and pdf files. Probably 90% of the code there is beyond what I need, but the semantics are so unlike anything I've ever come across (I'm miles away from image processing). I can't even figure where to start since everything seems so interconnected. Is there a simplest case example of Drag and drop which only serves file path extraction? From the aforementioned sample code I'm struggling to figure out what is the part which is absolutely needed only to retrieve the path? Do I have to init a [NSImage canInitWIthPasteboard: ... ...] if a file is a plain text file, or a raw data file? The app doesn't need to know what the file is, since passing the absolute path as text argument cannot do any harm in this case - the number crunching command line program takes care of the content. Do I need coders? Do I need a sourceOperationMaskForDragingContext? Does Drag and Drop even cover such trivial demands?
Thanks in advance!
Regards, UU

Answer 1

Thanks for your kind replay. Please let's stay on-topic: my question shouldn't have pointed at if "Apple works like this or like that".
IMHO, it's quit opposite: many things are cut-and-paste compatible, yet I'm missing few basic explanations.
The following code can be derived from the API reference:
#import "DragTView.h"
#import "AppDelegate.h"
@implementation DragTView
- (id)initWithFrame:(NSRect)frame{
    self = [super initWithFrame:frame];
    if (self) [self registerForDraggedTypes:[NSArray arrayWithObject:NSFilenamesPboardType]];
    return self;
- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender{
    highlight=YES;
    [self setNeedsDisplay: YES];
    return NSDragOperationGeneric;
- (void)draggingExited:(id <NSDraggingInfo>)sender{
    highlight=NO;
    [self setNeedsDisplay: YES];
- (void)drawRect:(NSRect)rect
    [super drawRect:rect];
    if ( highlight ) {
        [[NSColor grayColor] set];
        [NSBezierPath setDefaultLineWidth: 5];
        [NSBezierPath strokeRect: rect];
- (BOOL)prepareForDragOperation:(id <NSDraggingInfo>)sender {
    highlight=NO;
    [self setNeedsDisplay: YES];
    return YES;
- (BOOL)performDragOperation:(id < NSDraggingInfo >)sender {
    NSArray *draggedFilenames = [[sender draggingPasteboard] propertyListForType:NSFilenamesPboardType];
    NSURL* fileURL;
    NSTextField* pathField = [(AppDelegate*)[[NSApplication sharedApplication] delegate] pathField];
    if (([[[draggedFilenames objectAtIndex:0] pathExtension] isEqual:@"txt"]){
        fileURL=[NSURL URLFromPasteboard: [sender draggingPasteboard]];
        [pathField setStringValue:  [fileURL path] ];
        return YES;
    } else return NO;
- (void)concludeDragOperation:(id <NSDraggingInfo>)sender{
@end
It reveals the file path, yet, it boils down to fifty meaningless lines of code, since the pathField object (of class NSTextField) would itself reveal a dropped file's path without a single extra line of drag-and-drop code. What I find confusing is the following:
How should a drag operation be set up, so a text file can be dragged to the DragTView object (declared as @interface DragView: NSImageView <NSDraggingSource, NSDraggingDestination>), which would than show the image of file's icon (without dragged file itself being an image file)? This is rather unclear in the documentation, with all due respect to Apple.
Thanks in advance.