How to set a mail Subject in UIActivityViewController?

I want to set subject for email sharing in UIActivityViewController and also want to share in Twitter. I know in Twitter if we want to share — we need compress text to 140 chars. I checked many SO solutions, but nothing is working.

Is this issue fixed in latest iOS releases? Any other "working solutions"?

Check below code for the email for setting up your email subject:

UIActivityViewController* avc = [[UIActivityViewController alloc] initWithActivityItems:@[@"Your String to share"]
                                  applicationActivities:nil];
[avc setValue:@"Your email Subject" forKey:@"subject"];

avc.completionHandler = ^(NSString *activityType, BOOL completed) {
    // ...
};

Here the line

> [avc setValue:@"Your email Subject" forKey:@"subject"];

Makes the subject as "Your email Subject" if user picks email option in the UIActivityViewController.

I hope it helps...

It seems as though emreoktem's solution—sending setValue:forKey: to the UIActivityViewController—is undocumented.

On iOS 7 and later, you can implement the activityViewController:subjectForActivityType: method in an object conforming to the UIActivityItemSource protocol to do this in a way that is documented.

Here's a concrete solution for Swift 3.0+ based on the accepted answer. Note that, like the accepted answer, this is known to work only on the iOS Mail app and not necessarily other apps.

#Implementation:

class MessageWithSubject: NSObject, UIActivityItemSource {

    let subject:String
    let message:String

    init(subject: String, message: String) {
        self.subject = subject
        self.message = message
        
        super.init()
    }
    
    func activityViewControllerPlaceholderItem(_ activityViewController: UIActivityViewController) -> Any {
        return message
    }
    
    func activityViewController(_ activityViewController: UIActivityViewController, itemForActivityType activityType: UIActivityType) -> Any? {
        return message
    }
    
    func activityViewController(_ activityViewController: UIActivityViewController,
                                subjectForActivityType activityType: UIActivityType?) -> String {
        return subject
    }
}

#Usage:

Here's an example of usage. Note that it works well to use this as the first item in the activityItems array, and include any additional items to follow:

let message = MessageWithSubject(subject: "Here is the subject", message: "An introductory message")
let itemsToShare:[Any] = [ message, image, url, etc ]

let controller = UIActivityViewController(activityItems: itemsToShare, applicationActivities: nil)

For Swift 2.0+ & ios 8.0+

let title = "Title of the post"
let content = "Content of the post"
let objectsToShare = [title, content]

let activityVC = UIActivityViewController(activityItems: objectsToShare, applicationActivities: nil)      
activityVC.setValue(title, forKey: "Subject")
self.presentViewController(activityVC, animated: true, completion: nil)