Creating Finder’s “Open With” Contextual Menu

vira — Sun, 13 Mar 2011 15:03:21 +0000

Hello everyone and congrats with spring/Lion/iPad2! I haven’t written for such a long time and so many things have happened.

'Open With' Menu

Today I want to share with you my experience of creating the analog of “Open With” menu, similar to Finder’s one. I’ve tried to create the exact copy of this menu: default application, list of other apps and “Other…” option. I use this menu in the one of our projects – MacHider and you have take a look of how it works.

When I’ve started to implement the menu, I was a bit surprised that this isn’t common component…After googling I haven’t found any ready to use solutions. So here is how I’ve implemented it

To get the list of apps that can open specified file you can use LSCopyApplicationURLsForURL function. The second parameter to this function is role of the application: is it editor or viewer for this file. Default application could be obtained by calling LSGetApplicationForURL.

The core method in the presented below code is openWithMenuItemForFile. It returns NSMenu for specified file path and you can show this menu whenever and wherever you want. In our app I show it when system calls “validateMenuItem” for “Open With” menu item. Not the best solution, because user don’t necessary show this menu but it’s easy to implement and it works. Also I want to note, that building this menu takes some time. So be careful not to freeze UI.

 
- (void)openSelectedFileWithApplication:(NSString *)appPath
{
    NSString *filePath = file path, e.g. from selected table row>
    [[NSWorkspace sharedWorkspace] openFile:filePath withApplication:appPath];
}
 
/// menu item action
- (void)openWithApplicationSelected:(id)sender
{
    if (![sender isKindOfClass:[NSMenuItem class]]) {
        NSLog(@"Sender should be nsmenuitem");
        return;
    }
 
    NSMenuItem *menuItem = (NSMenuItem *)sender;
    NSString *appPath = [menuItem representedObject];
    if (!appPath) {
        NSLog(@"Could get app path from nsmenuitem represented object");
        return;
    }
    [self openSelectedFileWithApplication:appPath];
}
 
- (void)openWithApplicationOtherSelected:(id)sender
{
    NSOpenPanel *panel = [NSOpenPanel openPanel];
 
    [panel setAllowsMultipleSelection:NO];
    [panel setCanChooseFiles:YES];
    [panel setCanChooseDirectories:NO];
 
    [panel beginSheetForDirectory:@"/Applications"
                                               file:nil
                                            types:nil
                         modalForWindow:[mainController window]
                            modalDelegate:self
                            didEndSelector:@selector(chooseAppSheetClosed:returnCode:contextInfo:)
                                 contextInfo:nil];
}
 
- (void)chooseAppSheetClosed:(NSOpenPanel *)panel returnCode:(int)code contextInfo:(NSNumber *)useOptions
{
    if (code == NSOKButton)
    {
		[panel close];
                [self openSelectedFileWithApplication:[panel filename]];
    }
}
 
/// construct menu item for app
- (NSMenuItem *)menuItemForOpenWithForApplication:(NSString *)appName path:(NSString *)appPath
{
    NSMenuItem *newAppItem = [[[NSMenuItem alloc] init] autorelease];
    [newAppItem setTitle:appName];
    [newAppItem setTarget:self];
    [newAppItem setAction:@selector(openWithApplicationSelected:)];
    [newAppItem setRepresentedObject:appPath];
    [newAppItem setImage:[[[NSWorkspace sharedWorkspace] iconForFile:appPath] imageByScalingToSize:NSMakeSize(16, 16)]];
    return newAppItem;
}
 
/// this method return open with menu for specified file
- (NSMenu *)openWithMenuItemForFile:(NSString *)filePath
{
    NSMenu *subMenu = [[[NSMenu alloc] init] autorelease];
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];
   CFArrayRef cfArrayOfApps = LSCopyApplicationURLsForURL((CFURLRef)fileURL, kLSRolesAll);
    CFIndex maxCount = 10;
    NSMutableSet *alreadyAdded = [NSMutableSet setWithCapacity:maxCount];
	if (cfArrayOfApps != nil)
	{
		CFIndex count = CFArrayGetCount(cfArrayOfApps);
        if (count > maxCount) {
            count = maxCount;
        }
        //get and add default app
        CFURLRef defaultApp;
        LSGetApplicationForURL((CFURLRef)fileURL, kLSRolesAll, NULL, &defaultApp);
        if (!defaultApp) {
            NSLog(@"There is no default App for %@", filePath);
            NSMenuItem *noneItem = [[NSMenuItem alloc] init];
            [noneItem setTitle:@""];
            [noneItem setEnabled:NO];
            [subMenu addItem:noneItem];
            [noneItem release];
            [subMenu addItem:[NSMenuItem separatorItem]];
        }
        else {
            NSString *defaultAppPath = [(NSURL *)defaultApp path];
            NSString *defaultAppName = [[[defaultAppPath lastPathComponent] stringByDeletingPathExtension] stringByAppendingString:@" (default)"];
            NSMenuItem *newAppItem = [self menuItemForOpenWithForApplication:defaultAppName path:defaultAppPath];
            [subMenu addItem:newAppItem];
            [subMenu addItem:[NSMenuItem separatorItem]];
            if (count != 0) {
                for (int index = 0; index < count; ++index)
                {
                    NSURL *appURL = (NSURL *)CFArrayGetValueAtIndex(cfArrayOfApps, index);
                    if ([appURL isFileURL])
                    {
                        NSString *appName = [[[appURL path] lastPathComponent] stringByDeletingPathExtension];
                        if ([alreadyAdded containsObject:appName]) {
                            appName = [appName stringByAppendingFormat:@" (%@)", [[[NSBundle bundleWithPath:defaultAppPath] infoDictionary] valueForKey:@"CFBundleVersion"]];
                        }
                        NSMenuItem *newAppItem = [self menuItemForOpenWithForApplication:appName path:[appURL path]];
                        [alreadyAdded addObject:appName];
                        [subMenu addItem:newAppItem];
                    }
                }
                [subMenu addItem:[NSMenuItem separatorItem]];
            }            
        }
 
        NSMenuItem *otherAppItem = [[[NSMenuItem alloc] init] autorelease];
        [otherAppItem setTitle:@"Other…"];
        [otherAppItem setTarget:self];
        [otherAppItem setAction:@selector(openWithApplicationOtherSelected:)];
        [subMenu addItem:otherAppItem];
 
	CFRelease(cfArrayOfApps);
    }
    return subMenu;
}

Cocoa Tip: Filtering NSArray using NSPredicate

vira — Tue, 12 Jan 2010 22:13:35 +0000

Today I’ve had a small task in one of my projects – to get subset of elements from NSArray. I’ve already started writing all this NSEnumerator’s stuff (need to support 10.4) when I remembered about NSPredicator. So, instead of iterating over an array and finding elements that satisfy some condition and adding them to some output array you just need to create predicate and filter your input array with it. Here is the sample code:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"storeState == 1"];
NSArray  *outputArray = [inputArray filteredArrayUsingPredicate:predicate];

Predicates language seems to be very powerful and simple. But I can’t tell you anything about performance, need to investigate.

UPDATE If you want to filter array with regular expressions just use a predicate like this one:

[NSPredicate predicateWithFormat:@"SELF MATCHES %@", regexp];

Further reading: Apple Predicates Programming Guide

iVira.name » cocoa

Creating Finder’s “Open With” Contextual Menu

Cocoa Tip: Filtering NSArray using NSPredicate