Swift で UIActivityViewController を利用してfacebookやTwitterにシェアをする ref: http://qiita.com/matsuhisa@github/items/7a599e0276cfabe1090e

file0.swift

ButtonShare.addTarget(self, action: "share_action:", forControlEvents: .TouchUpInside)

file1.swift

// 長押し
var myLongPressGesture = UILongPressGestureRecognizer(target: self, action: "lognPress:")

// 長押し - 2.0秒
myLongPressGesture.minimumPressDuration = 2.0
// 長押し - 許容範囲15px
myLongPressGesture.allowableMovement = 150

// 画像に長押しがあったときの対応
SampleImage.userInteractionEnabled = true
SampleImage.addGestureRecognizer(myLongPressGesture)

file2.swift

import UIKit
import Social

class DetailViewController: UIViewController {

    @IBOutlet weak var detailDescriptionLabel: UILabel!
    @IBOutlet weak var ButtonShare: UIButton!
    @IBOutlet weak var SampleImage: UIImageView!

    func configureView() {
        if let detail: AnyObject = self.detailItem {
            if let label = self.detailDescriptionLabel {
                label.text = detail.description
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.configureView()

        // 長押し
        var myLongPressGesture = UILongPressGestureRecognizer(target: self, action: "lognPress:")

        // 長押し - 2.0秒
        myLongPressGesture.minimumPressDuration = 2.0

        // 長押し - 許容範囲15px
        myLongPressGesture.allowableMovement = 150

        // 画像に長押しがあったときの対応
        SampleImage.userInteractionEnabled = true
        SampleImage.addGestureRecognizer(myLongPressGesture)

        // share
        ButtonShare.addTarget(self, action: "share_action:", forControlEvents: .TouchUpInside)
    }

    func lognPress(sender: UILongPressGestureRecognizer) {
        println("lognPress")
        share_action(self)
    }

    func share_action(sender: AnyObject) {
        println("share_action")

        let secondActivityItem = "iOSからのテストです #桜"
        let firstActivityItem:UIImage = SampleImage.image! as UIImage

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


        activityViewController.completionWithItemsHandler = {(activityType, completed:Bool, returnedItems:Array!, error:NSError!) in
            if (completed) {
                // ここに完了後の処理を書く
                println("完了！")
            }
        }

        self.presentViewController(activityViewController, animated: true, completion: nil)
    }