DecimalMinusTextField.swift

//
//  DecimalMinusTextField.swift
//
//  Created by Jonathan Engelsma on 9/24/15.
//  Copyright (c) 2015 Jonathan Engelsma. All rights reserved.
//

import UIKit

/**
    An extension to UITextField that augments the standard decimal keypad with
    a minus button and a done button.  The implementation was inspired by this 
    particular question/answer thread:
        http://stackoverflow.com/questions/9613109/uikeyboardtypedecimalpad-with-negative-numbers
*/
class DecimalMinusTextField: UITextField {
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        self.keyboardType = UIKeyboardType.decimalPad

    }
    
    fileprivate func getAccessoryButtons() -> UIView
    {
        let view = UIView(frame: CGRect(x: 0, y: 0, width: self.superview!.frame.size.width, height: 44))
        view.backgroundColor = UIColor.lightGray
        
        let minusButton = UIButton(type: UIButton.ButtonType.custom)
        let doneButton = UIButton(type: UIButton.ButtonType.custom)
        minusButton.setTitle("-", for: UIControl.State())
        doneButton.setTitle("Done", for: UIControl.State())
        let buttonWidth = view.frame.size.width/3;
        minusButton.frame = CGRect(x: 0, y: 0, width: buttonWidth, height: 44);
        doneButton.frame = CGRect(x: view.frame.size.width - buttonWidth, y: 0, width: buttonWidth, height: 44);
        
        minusButton.addTarget(self, action: #selector(DecimalMinusTextField.minusTouchUpInside(_:)), for: UIControl.Event.touchUpInside)
        doneButton.addTarget(self, action: #selector(DecimalMinusTextField.doneTouchUpInside(_:)), for: UIControl.Event.touchUpInside)
        
        view.addSubview(minusButton)
        view.addSubview(doneButton)
        
        return view;
    }
    
    @objc func minusTouchUpInside(_ sender: UIButton!) {

        let text = self.text!
        if(text.count > 0) {
            let index: String.Index = text.index(text.startIndex, offsetBy: 1)
            let firstChar = text[..<index]
            if firstChar == "-" {
                self.text = String(text[index...])
            } else {
                self.text = "-" + text
            }
        }
    }
    
    @objc func doneTouchUpInside(_ sender: UIButton!) {
        self.resignFirstResponder();
        
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        self.inputAccessoryView = getAccessoryButtons()
    }


}