swift example for learning according to the link below :
- https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/index.html#//apple_ref/doc/uid/TP40014097-CH3-XID_0
- https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/index.html#//apple_ref/doc/uid/TP40014216-CH2-XID_0
- http://www.weheartswift.com/make-awesome-ui-components-ios-8-using-swift-xcode-6/