A basic Share Extension Test created by combining two simple test cases. Contains the ShareViewController for the extension and the index controller and view for the Titanium Project

index.js

var appGroupId = 'group.com.YourGroupId';

var props = Ti.App.iOS.createUserDefaults({
    suiteName: appGroupId
});
var score = props.getInt('score');
if (!score)
	score = 1;
props.setInt('score', score);



// Get the shared container path
var sharedPath = Ti.Filesystem.directoryForSuite(appGroupId);
 
// Copy a file from the application to the shared container
var appFile = Ti.Filesystem.getFile(sharedPath, 'somesharefile.txt');
Ti.API.error(appFile);

function doClick(e) {
	score = props.getInt('score');
	Ti.API.error("++++++++++ score was: "+score);
	
	score += 1;
	props.setInt('score', score);
	Ti.API.error("++++++++++ score is: "+props.getInt('score'));
	
	if (appFile.createFile())
		appFile.write("Hello");
	Ti.API.error("++++++++++ data was: "+appFile.read());
	
    
	appFile.write($.text.value);
	Ti.API.error("++++++++++ data is: "+appFile.read());
}

function getImages(e) {
	var dir = Ti.Filesystem.getFile(sharedPath);
	var dir_files = dir.getDirectoryListing();
	var views = [];
    for (var i=0;i<dir_files.length;i++){ 
        if (dir_files[i].indexOf("image") == -1)
        	continue;
        var view = Ti.UI.createImageView({
        	image: Ti.Filesystem.getFile(sharedPath, dir_files[i])
        });
        views.push(view);
    }
    $.scroll.views = views;
}

$.index.open();

index.xml

<Alloy>
    <Window class="container">
        <TextField id="text" borderColor="black" top="30%" value="This is from the app" />
        <Button onClick="doClick" top="40%">OK</Button>
        <Button onClick="getImages" top="50%">Get Images</Button>
        <ScrollableView id="scroll" showPagingControl="true" top="60%" height="40%"/>
    </Window>
</Alloy>

Share Extension

A basic Share Extension Test created by combining two simple test cases. Contains the ShareViewController for the extension and the index controller and view for the Titanium Project

ShareViewController.m

#import "ShareViewController.h"
@import MobileCoreServices;


static NSString *const AppGroupId = @"group.com.YourGroupId";
static NSString *const AppName = @"YourAppName";


@interface ShareViewController ()

@end

@implementation ShareViewController

NSUInteger m_inputItemCount = 0;
NSString * m_invokeArgs = NULL;
NSUserDefaults *sharedUserDefaults;
NSURL *groupURL;
NSExtensionItem *inputItem;

- (BOOL)isContentValid
{
    // Do validation of contentText and/or NSExtensionContext attachments here
    return YES;
}

-(void)viewDidLoad
{
    // Get and print the Score key from user defaults
    sharedUserDefaults = [[NSUserDefaults alloc] initWithSuiteName:AppGroupId];
    NSNumber *score = [NSNumber numberWithDouble:[sharedUserDefaults doubleForKey:@"score"]];
    NSLog(@"++++++++++ score was: %@", score);
    
    // Read and print the contents of 'somesharefile.txt' in the shared container
    groupURL = [[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:AppGroupId];
    NSString *docPath = [groupURL.path stringByAppendingPathComponent:@"somesharefile.txt"];
    
    NSString *oldData = [[NSString alloc] initWithData:[NSData dataWithContentsOfFile:docPath] encoding:NSUTF8StringEncoding];
    NSLog(@"++++++++++ data was: %@", oldData);
}

- (void)didSelectPost
{
    // Write and print the contents of 'somesharefile.txt' in the shared container
    NSString *docPath = [groupURL.path stringByAppendingPathComponent:@"somesharefile.txt"];
    NSString *data = @"I came from the extension";
    [data writeToFile:docPath atomically:YES encoding:NSUTF8StringEncoding error:NULL];
    
    data = [[NSString alloc] initWithData:[NSData dataWithContentsOfFile:docPath] encoding:NSUTF8StringEncoding];
    NSLog(@"++++++++++ data is: %@", data);
    
    // Check the attachment type
    inputItem = self.extensionContext.inputItems.firstObject;
    
    NSItemProvider *urlItemProvider = [[inputItem.userInfo valueForKey:NSExtensionItemAttachmentsKey] objectAtIndex:0];
    
    if ([urlItemProvider hasItemConformingToTypeIdentifier:(__bridge NSString *)kUTTypeURL])
    {
        // Handle a URL attachment. Write it to user defaults
        NSLog(@"++++++++++ Attachment is a URL");
        
        [urlItemProvider loadItemForTypeIdentifier:(__bridge NSString *)kUTTypeURL options:nil completionHandler:^(NSURL *url, NSError *error)
         {
             if (error)
             {
                 NSLog(@"Error occured");
             }
             else
             {
                 NSMutableArray *arrSites;
                 if ([sharedUserDefaults valueForKey:@"SharedExtension"])
                     arrSites = [sharedUserDefaults valueForKey:@"SharedExtension"];
                 else
                     arrSites = [[NSMutableArray alloc] init];
                 NSDictionary *dictSite = [NSDictionary dictionaryWithObjectsAndKeys:self.contentText, @"Text", url.absoluteString, @"URL",nil];
                 [arrSites addObject:dictSite];
                 [sharedUserDefaults setObject:arrSites forKey:@"SharedExtension"];
                 [sharedUserDefaults synchronize];
             }
         }];
    } else {
        NSLog(@"++++++++++ Attachment is not a URL");
        [ self passSelectedItemsToApp ];
    }
    
    
}

- (NSArray *)configurationItems {
    // To add configuration options via table cells at the bottom of the sheet, return an array of SLComposeSheetConfigurationItem here.
    return @[];
}

- ( void ) addImagePathToArgumentList: ( NSString * ) imagePath
{
    assert( NULL != imagePath );
    
    // The list of arguments we will pass to the AIR app when we invoke it.
    // It will be a comma-separated list of file paths: /path/to/image1.jpg,/path/to/image2.jpg
    if ( NULL == m_invokeArgs )
    {
        m_invokeArgs = imagePath;
    }
    else
    {
        m_invokeArgs = [ NSString stringWithFormat: @"%@,%@", m_invokeArgs, imagePath ];
    }
}

- ( NSString * ) saveImageToAppGroupFolder: ( UIImage * ) image
                                imageIndex: ( int ) imageIndex
{
    assert( NULL != image );
    
    NSData * jpegData = UIImageJPEGRepresentation( image, 1.0 );
    
    NSString * documentsPath = groupURL.path;
    
    // Note that we aren't using massively unique names for the files in this example:
    NSString * fileName = [ NSString stringWithFormat: @"image%d.jpg", imageIndex ];
    
    NSString * filePath = [ documentsPath stringByAppendingPathComponent: fileName ];
    [ jpegData writeToFile: filePath atomically: YES ];
    
    [sharedUserDefaults synchronize];
    
    return filePath;
}

- ( void ) passSelectedItemsToApp
{
    NSExtensionItem * item = self.extensionContext.inputItems.firstObject;
    
    // Reset the counter and the argument list for invoking the app:
    m_invokeArgs = NULL;
    m_inputItemCount = item.attachments.count;
    
    // Iterate through the attached files
    for ( NSItemProvider * itemProvider in item.attachments )
    {
        // Check if we are sharing a Image
        if ( [ itemProvider hasItemConformingToTypeIdentifier: ( NSString * ) kUTTypeImage ] )
        {
            NSLog(@"++++++++++ Attachment is an Image");
            
            // Load it, so we can get the path to it
            [ itemProvider loadItemForTypeIdentifier: ( NSString * ) kUTTypeImage
                                             options: NULL
                                   completionHandler: ^ ( UIImage * image, NSError * error )
             {
                 static int itemIdx = 0;
                 
                 if ( NULL != error )
                 {
                     NSLog( @"There was an error retrieving the attachments: %@", error );
                     return;
                 }
                 
                 // The app won't be able to access the images by path directly in the Camera Roll folder,
                 // so we temporary copy them to a folder which both the extension and the app can access:
                 NSString * filePath = [ self saveImageToAppGroupFolder: image imageIndex: itemIdx ];
                 
                 // Now add the path to the list of arguments we'll pass to the app:
                 [ self addImagePathToArgumentList: filePath ];
                 
                 // If we have reached the last attachment, it's time to hand control to the app:
                 if ( ++itemIdx >= m_inputItemCount )
                 {
                     [ self invokeApp: m_invokeArgs ];
                 }
             } ];
        }
        else
        {
            NSLog(@"++++++++++ Attachment is not an Image");
        }
    }
}
- ( void ) invokeApp: ( NSString * ) invokeArgs
{
    // Prepare the URL request
    // this will use the custom url scheme of your app
    // and the paths to the photos you want to share:
    NSString * urlString = [ NSString stringWithFormat: @"%@://%@", AppName,( NULL == invokeArgs ? @"" : invokeArgs ) ];
    NSURL * url = [ NSURL URLWithString: urlString ];
    
    NSString *className = @"UIApplication";
    if ( NSClassFromString( className ) )
    {
        id object = [ NSClassFromString( className ) performSelector: @selector( sharedApplication ) ];
        [ object performSelector: @selector( openURL: ) withObject: url ];
    }
    
    // Now let the host app know we are done, so that it unblocks its UI:
    [ super didSelectPost ];
}

@end

tiapp.xml

<!-- Replace items in [] -->

<ios>
    <team-id>[TEAM ID HERE]</team-id>
    <capabilities>
        <app-groups>
            <group>[group.com.YourGroupId]</group>
        </app-groups>
    </capabilities>
    <extensions>
        <extension projectPath="[Path to extension's .xcodeproj]">
            <target name="[Target Name]">
                <provisioning-profiles>
                    <device>[Device-UDID]</device>
                    <dist-appstore/>
                    <dist-adhoc/>
                </provisioning-profiles>
            </target>
        </extension>
    </extensions>
    <key>NSExtensionAttributes</key>
    <dict>
        <key>NSExtensionActivationRule</key>
        <dict>
            <key>NSExtensionActivationSupportsImageWithMaxCount</key>
            <integer>10</integer>
            <key>NSExtensionActivationSupportsMovieWithMaxCount</key>
            <integer>1</integer>
            <key>NSExtensionActivationSupportsWebURLWithMaxCount</key>
            <integer>1</integer>
        </dict>
    </dict>
    <plist>
        <dict>
            <key>CFBundleURLTypes</key>
            <array>
                <dict>
                    <key>CFBundleTypeRole</key>
                    <string>Editor</string>
                    <key>CFBundleURLName</key>
                    <string>[com.Your.AppId]</string>
                </dict>
            </array>
        </dict>
    </plist>
</ios>

Great. Would have been good if tiapp.xml was included too.