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UIActivityViewController was introduced in iOS 6 for apps to handle data (text, url, image, etc) in another app.

Share a text and URL

One of the most common scenario is to share a URL, accompanied by some text. It could be accomplished with this code:

let textToShare = "Hello world"
let urlToShare = NSURL(string: "http://samwize.com")
let activityViewController = UIActivityViewController(activityItems: [textToShare, urlToShare!], applicationActivities: nil)
// Exclude irrelevant activities
activityViewController.excludedActivityTypes =
    [UIActivityTypeAssignToContact, UIActivityTypeSaveToCameraRoll, UIActivityTypePostToFlickr,
        UIActivityTypePostToVimeo, UIActivityTypeOpenInIBooks]
navigationController?.presentViewController(activityViewController, animated: true, completion: nil)

UIActivityItemSource

Things are never so simple..

• Mail will not have a subject, because you never specify one
• In Message/Mail/etc, the content will have the text, followed by the URL (it looks bad if the text already contains the URL)

The better, more advanced way, is to implement UIActivityItemSource for your view controller.

By implementing the protocol, you can change the string to returning, depending on what activity it is. You could even return different types (String/UIImage/etc).

func activityViewControllerPlaceholderItem(activityViewController: UIActivityViewController) -> AnyObject {
    return "Hello World"
}

func activityViewController(activityViewController: UIActivityViewController, itemForActivityType activityType: String) -> AnyObject? {
    switch activityType {

    case let x where [UIActivityTypePostToFacebook, UIActivityTypePostToTwitter].contains(x):
        // Returns text for social media services
        return "Sharing with you.. hello world!"

    case UIActivityTypeMail:
        // Returns long text for email
        return "Hello World~~~~~~~~~~~~~~~~~~"

    case let x where [UIActivityTypeCopyToPasteboard].contains(x):
        // Returns url
        let url = NSURL(string: "http://samwize.com")
        return url!

    default:
        return "Hello World"
    }
}

func activityViewController(activityViewController: UIActivityViewController, subjectForActivityType activityType: String?) -> String {
    return "Hello Subject"
}

func activityViewController(activityViewController: UIActivityViewController, thumbnailImageForActivityType activityType: String?, suggestedSize size: CGSize) -> UIImage? {
    return UIImage(named: "hello")
}

With that, you now init UIActivityViewController with your view controller.

let activityViewController = UIActivityViewController(activityItems: [self], applicationActivities: nil)

Sharing directly to Facebook/Twitter using SLComposeViewController

Instead of using UIActivityViewController, which has the extra step of prompting user which app to use, SLComposeViewController can be used if all you want is post to Facebook/Twitter/etc.

Sharing directly using their url scheme

Another way to open an app to share data is via the app’s url scheme.

For example, WhatsApp provided a simple url scheme to send text:

whatsapp://send?text=Hello%2C%20World!

Pitfall: Starting from iOS 9, Apple changed the way we can open URL. You need to add to Info.plist the key LSApplicationQueriesSchemes, which is an array containing the URL schemes that can be opened. For example, to open WhatsApp, add “whatsapp” to the array.

If your text to share includes a URL eg. “Visit http://samwize.com today!”, then this URL encoding tips is for you:

let set = NSCharacterSet.URLQueryAllowedCharacterSet().mutableCopy() as! NSMutableCharacterSet
set.removeCharactersInString(":/?=")    // Encode these too!
guard let encodedShareText = shareText.stringByAddingPercentEncodingWithAllowedCharacters(set) else { return }
guard let url = NSURL(string: "whatsapp://send?text=\(encodedShareText)") else { return }

if UIApplication.sharedApplication().canOpenURL(url) {
    UIApplication.sharedApplication().openURL(url)
} else {
    // Cannot open WhatsApp
}

UIDocumentInteractionController

To share an image to WhatsApp is more difficult. You will need to use UIDocumentInteractionController.

Other Notes

• Facebook does not allow the text (aka status) to be programatically changed when using SLComposeViewController or UIActivityViewController. However, if you use their Facebook SDK, then you can change the text..