There's a section about this in the author's medium article https://medium.com/@samvlu/100-days-of-swift-the-tutorials-ddd8c17c1594#.9vryfzygi https://medium.

There's a section about this in the author's medium article https://medium.com/@samvlu/100-days-of-swift-the-tutorials-ddd8c17c1594#.9vryfzygi https://medium.com/@samvlu/100-days-of-swift-the-tutorials-d...