UILabelでタグっぽい見た目を実装する

import UIKit

class TagLabel: UILabel {

    let tagPadding: CGFloat = 5

    override init(frame: CGRect) {
        super.init(frame: frame)

        layer.cornerRadius = 2
        layer.borderColor = UIColor.blackColor().CGColor
        layer.borderWidth = 1
        textColor = UIColor.blackColor()
        clipsToBounds = true
        numberOfLines = 1
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func drawRect(rect: CGRect) {
        let insets = UIEdgeInsets(top: tagPadding, left: tagPadding, bottom: tagPadding, right: tagPadding)
        return super.drawTextInRect(UIEdgeInsetsInsetRect(rect, insets))
    }

}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let tagFont = UIFont.systemFontOfSize(16)
        let tagHeight = tagFont.lineHeight + TagLabel().tagPadding * 2
        let tagText = "hoge"
        let tagWidth = tagLabelTextWidth(text: tagText, font: tagFont, height: tagHeight)
        let tag = TagLabel(frame: CGRectMake(100, 100, tagWidth, tagHeight))
        tag.text = tagText
        tag.font = tagFont
        view.addSubview(tag)
    }

    func tagLabelTextWidth(text text: String, font: UIFont, height: CGFloat) -> CGFloat {
        let label = UILabel(frame: CGRectMake(0, 0, CGFloat.max, height))
        label.font = font
        label.text = text
        label.sizeToFit()
        return label.frame.size.width + TagLabel().tagPadding * 2
    }

}

let words = [
    "Ruby",
    "Ruby on Rails",
    "JavaScript",
    "Swift",
    "iOS",
    "HTML",
    "CSS",
    "Perl",
    "Python",
    "PHP",
    "Java",
    "Scala",
    "Go",
    "Elixir",
    "Objective-C"
]

override func viewDidLoad() {
    super.viewDidLoad()

    // (略)

    let tagsView = UIView(frame: CGRectMake(50, 200, view.bounds.size.width - 50 * 2, 200))  // 高さは適当な大きさに
    view.addSubview(tagsView)
    placeTagsOn(tagsView, tags: words)
}

func placeTagsOn(tagsView: UIView, tags: [String]) {
    let areaWidth = tagsView.bounds.size.width
    let tagMargin: CGFloat = 10
    let tagFont = UIFont.systemFontOfSize(16)
    let tagHeight = tagFont.lineHeight + TagLabel().tagPadding * 2

    var tagOriginX: CGFloat = 0
    var tagOriginY: CGFloat = 0

    for tag in tags {
        var tagWidth = tagLabelTextWidth(text: tag, font: tagFont, height: tagHeight)
        if tagWidth > areaWidth {
            tagWidth = areaWidth
        }

        if areaWidth - tagOriginX < tagWidth {
            tagOriginX = 0
            tagOriginY += tagHeight + tagMargin
        }

        let label = TagLabel(frame: CGRectMake(tagOriginX, tagOriginY, tagWidth, tagHeight))
        label.text = tag
        label.font = tagFont
        tagsView.addSubview(label)

        tagOriginX += tagWidth + tagMargin
    }
}