RadialView

//
//  RadialView.swift
//  
//
//  Created by John Rommel Estropia on 2016/08/06.
//  Copyright © 2016 JohnEstropia. All rights reserved.
//
import UIKit


// MARK: - RadialView
class RadialView: UIView {
    
    var innerColor = UIColor.clear {
        
        didSet {
            
            self.setNeedsDisplay()
        }
    }
    
    var outerColor = UIColor.clear {
        
        didSet {
            
            self.setNeedsDisplay()
        }
    }
    
    var innerOffset: CGFloat = 0 {
        
        didSet {
            
            self.setNeedsDisplay()
        }
    }
    
    var outerOffset: CGFloat = 1 {
        
        didSet {
            
            self.setNeedsDisplay()
        }
    }
    
    override init(frame: CGRect) {
        
        super.init(frame: frame)
        self.setup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        
        super.init(coder: aDecoder)
        self.setup()
    }
    
    
    // MARK: NSObject
    
    override func awakeFromNib() {
        
        super.awakeFromNib()
        self.setup()
    } 
    
    
    // MARK: UIView
    
    override func draw(_ rect: CGRect) {
        
        let startCenter = CGPoint(x: rect.midX, y: rect.midY)
        let endCenter = startCenter
        
        let startRadius: CGFloat = 0
        let endRadius = hypot(startCenter.x, startCenter.y)
        
        let locations = [self.innerOffset, self.outerOffset]
        var components = Array<CGFloat>(repeating: 0, count: 8);
        
        do {
            
            let innerColor = self.innerColor.cgColor
            if innerColor.numberOfComponents == 4 {
                
                let partialComponents = innerColor.components!
                components[0] = partialComponents[0]
                components[1] = partialComponents[1]
                components[2] = partialComponents[2]
                components[3] = partialComponents[3]
            }
            else {
                
                let partialComponents = innerColor.components!
                components[0] = partialComponents[0]
                components[1] = partialComponents[0]
                components[2] = partialComponents[0]
                components[3] = partialComponents[1]
            }
        }
        do {
            
            let outerColor = self.outerColor.cgColor
            if outerColor.numberOfComponents == 4 {
                
                let partialComponents = outerColor.components!
                components[4] = partialComponents[0]
                components[5] = partialComponents[1]
                components[6] = partialComponents[2]
                components[7] = partialComponents[3]
            }
            else {
                
                let partialComponents = outerColor.components!
                components[4] = partialComponents[0]
                components[5] = partialComponents[0]
                components[6] = partialComponents[0]
                components[7] = partialComponents[1]
            }
        }
        UIGraphicsGetCurrentContext()?.drawRadialGradient(CGGradient(colorSpace: CGColorSpaceCreateDeviceRGB(), colorComponents: components, locations: locations, count: 2)!,
            startCenter: startCenter,
            startRadius: startRadius,
            endCenter: endCenter,
            endRadius: endRadius,
            options: .drawsAfterEndLocation
        )
    }
    

    // MARK: Private
    
    private func setup() {
        
        self.contentMode = .redraw
    }
}