ControlBar

SOTControlBar.Swift

//
//  SOTControlBar.swift
//  ControlBar
//
//  Created by Andrea Altea on 27/06/17.
//  Copyright © 2017 StudiOUT. All rights reserved.
//

import UIKit

class SOTControlBar: UIView {

    var components: Array<UIView>? {
        
        willSet {
            
            guard let oldComponents = self.components else {
                return
            }
            
            oldComponents.forEach({ (component) in
                component.removeFromSuperview()
            })
        }
        
        didSet {
    
            guard let components = self.components else {
                return
            }
            
            for index in 0 ..< components.count {
                
                let component = components[index]
                component.translatesAutoresizingMaskIntoConstraints = false
                self.addSubview(component)
                
                self.setConstraints(for: component, with: index > 0 ? components[index-1] : nil)
            }
            
            guard let lastComponent = components.last else {
                return
            }
            
            let rightConstraint = NSLayoutConstraint.constraint(from: lastComponent, to: self, with: .right)
            self.addConstraint(rightConstraint)
        }
    }
    
    private func setConstraints(for component: UIView, with previous: UIView?) {
        
        let vConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:|-0-[component]-0-|", options: NSLayoutFormatOptions(rawValue:0), metrics: nil, views: ["component" : component])
        self.addConstraints(vConstraints)
        
        guard let previous = previous else {

            let leftConstraint = NSLayoutConstraint.constraint(from: self, to: component, with: .left)
            self.addConstraint(leftConstraint)
            return
        }
        
        let widthConstraint = NSLayoutConstraint.constraint(from: component, to: previous, with: .width)
        self.addConstraint(widthConstraint)
        
        let leftConstraint = NSLayoutConstraint(item: component, attribute: .left, relatedBy: .equal, toItem: previous, attribute: .right, multiplier: 1, constant: 0)
        self.addConstraint(leftConstraint)
    }
}

fileprivate extension NSLayoutConstraint {
    
    static func constraint(from fromComponent: UIView, to toComponent: UIView, with attribute: NSLayoutAttribute) -> NSLayoutConstraint {
        
        return NSLayoutConstraint(item: fromComponent, attribute: attribute, relatedBy: .equal, toItem: toComponent, attribute: attribute, multiplier: 1, constant: 0)
    }
}