Cocoa/Obj-C - Open file when dragging it to application icon - objective-c

Question

Currently there is a button on my app inteface which allow to open a file, here is my open code:
In my app.h:
- (IBAction)selectFile:(id)sender;
In my app.m:
#synthesize window;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
}
- (IBAction)selectFile:(id)sender {
NSOpenPanel *openPanel = [NSOpenPanel openPanel];
NSArray *fileTypes = [NSArray arrayWithObjects:#"xml",nil];
NSInteger result = [openPanel runModalForDirectory:NSHomeDirectory() file:nil types:fileTypes ];
if(result == NSOKButton){
NSString * input = [openPanel filename];
How can I edit my code to allow opening with the application-icon drag & drop?
Note: I edited the .plist file and added a line for "xml" but it change anything, got an error when my file is dropped on the icon.
Note 2: I linked the "File -> Open..." to the selectFile: wich refer to my code
Note 3: My app isn't a document-based application
Thanks for your help!
Miskia

Answer 1

First add the proper extensions to CFBundleDocumentTypes inside the .plist file.
Next implement the following delegates:
- application:openFile: (one file dropped)
- application:openFiles: (multiple files dropped)
Reference:
NSApplicationDelegate Protocol Reference
Response to comment:
Step by step example, hopefully it makes everything clear :)
Add to the .plist file:
<key>CFBundleDocumentTypes</key>
<array>
<dict>
<key>CFBundleTypeExtensions</key>
<array>
<string>xml</string>
</array>
<key>CFBundleTypeIconFile</key>
<string>application.icns</string>
<key>CFBundleTypeMIMETypes</key>
<array>
<string>text/xml</string>
</array>
<key>CFBundleTypeName</key>
<string>XML File</string>
<key>CFBundleTypeRole</key>
<string>Viewer</string>
<key>LSIsAppleDefaultForType</key>
<true/>
</dict>
</array>
Add to ...AppDelegate.h
- (BOOL)processFile:(NSString *)file;
- (IBAction)openFileManually:(id)sender;
Add to ...AppDelegate.m
- (IBAction)openFileManually:(id)sender;
{
NSOpenPanel *openPanel = [NSOpenPanel openPanel];
NSArray *fileTypes = [NSArray arrayWithObjects:#"xml",nil];
NSInteger result = [openPanel runModalForDirectory:NSHomeDirectory() file:nil types:fileTypes ];
if(result == NSOKButton){
[self processFile:[openPanel filename]];
}
}
- (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filename
{
return [self processFile:filename];
}
- (BOOL)processFile:(NSString *)file
{
NSLog(#"The following file has been dropped or selected: %#",file);
// Process file here
return YES; // Return YES when file processed succesfull, else return NO.
}

Answer 2

for a quick&dirty solution:
Cocoa: Drag and Drop any file type
Tested under Xcode Version 11.4 (11E146)
catalina 10.15.4 (19E266)