User icon lining up view like FourSquare

CNLiningUpView.swift

//
//  CNLiningUpView.swift
//  CNLiningUpView
//
//  Created by Chiharu Nameki on 2015/03/29.
//  Copyright (c) 2015 Chiharu Nameki. All rights reserved.
//

import UIKit

class CNLiningUpItem {
    let imageURL: NSURL?
    let badgeImage: UIImage?
    init(imageURL: NSURL? = nil, badgeImage: UIImage? = nil) {
        self.imageURL = imageURL
        self.badgeImage = badgeImage
    }
}

class CNLiningUpItemView : UIView {
    var imageView: UIImageView!
    var badgeImageView: UIImageView!
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    
    func setup() {
        imageView = UIImageView(frame: bounds)
        imageView.contentMode = .ScaleAspectFill
        imageView.autoresizingMask = .FlexibleWidth | .FlexibleHeight
        imageView.clipsToBounds = true
        imageView.layer.cornerRadius = 2.0
        self.addSubview(imageView)
        badgeImageView = UIImageView(frame: CGRectMake(-2, -2, 10, 10))
        badgeImageView.autoresizingMask = .FlexibleRightMargin | .FlexibleBottomMargin
        self.addSubview(badgeImageView)
    }
}

class CNLiningUpView : UIView {
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    // data source
    var items: [CNLiningUpItem] = []
    var count: Int = 0

    // appearances
    var itemSize: CGSize = CGSizeMake(22, 22)
    var itemPlaceholderImage: UIImage?
    var margin: CGFloat = 4.0
    var showsMoreItem = true
    var badgeFrame: CGRect = CGRectMake(-2, -2, 10, 10)
    
    func reloadData() {
        update()
        for (i, itemView) in enumerate(itemViews) {
            if itemView.superview == nil {
                break
            }
            configureItemView(itemView, item:items[i])
        }
    }
    
    func generateItemView() -> UIView {
        let view = CNLiningUpItemView(frame: CGRectMake(0, 0, itemSize.width, itemSize.height))
        view.badgeImageView.frame = badgeFrame
        return view
    }
    
    func configureItemView(itemView: UIView, item: CNLiningUpItem) {
        if let itemView = itemView as? CNLiningUpItemView {
            itemView.imageView.sd_setImageWithURL(item.imageURL,
                placeholderImage: itemPlaceholderImage,
                options: .CacheMemoryOnly)
            itemView.badgeImageView.image = item.badgeImage
        }
    }
    
    func generateMoreItemView() -> UIView {
        let label = UILabel(frame: CGRectMake(0, 0, itemSize.width, itemSize.height))
        label.font = UIFont.systemFontOfSize(itemSize.height * 0.38)
        label.minimumScaleFactor = 0.5
        label.textColor = UIColor.whiteColor()
        label.textAlignment = .Center
        label.backgroundColor = UIColor.grayColor()
        return label
    }
    
    func configureMoreItemView(number: Int) {
        if let label = moreItemView as? UILabel {
            label.text = number < 100 ? "+\(number)" : "+lots"
        }
    }
    
    private var itemViews: [UIView] = []
    var moreItemView: UIView!
    
    override func layoutSubviews() {
        update()
    }
    
    private func update() {
        let centerY = (bounds.size.height - itemSize.height) * 0.5
        
        let max = Int((bounds.size.width + margin) / (itemSize.width + margin))
        let needsMoreItem = { () -> Bool in
            if self.showsMoreItem {
                if self.items.count < self.count {
                    return true
                }
                if max < self.items.count {
                    return true
                }
            }
            return false
        }()
        let n = min(min(items.count, count), max - (needsMoreItem ? 1 : 0))
        
        for i in 0..<n {
            if itemViews.count <= i {
                let itemView = generateItemView()
                itemViews.append(itemView)
                configureItemView(itemView, item: items[i])
            }
            
            let view = itemViews[i]
            view.frame = CGRectMake((itemSize.width + margin) * CGFloat(i), centerY, itemSize.width, itemSize.height)
            if view.superview == nil {
                addSubview(view)
            }
        }
        
        if n < itemViews.count {
            for i in n..<itemViews.count {
                let view = itemViews[i]
                view.removeFromSuperview()
            }
        }
        
        if needsMoreItem {
            if moreItemView == nil {
                moreItemView = generateMoreItemView()
            }
            
            moreItemView.frame = CGRectMake((itemSize.width + margin) * CGFloat(n), centerY, itemSize.width, itemSize.height)
            configureMoreItemView(count - n)
            
            if moreItemView.superview == nil {
                addSubview(moreItemView)
            }
        } else {
            moreItemView?.removeFromSuperview()
        }
    }
}