TextFieldExtension.swift

// Copyright © 2017 Kalpesh Talkar. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//  For support: https://gist.github.com/KalpeshTalkar/0ec476fd56de0c8caebc000ea4f17247
//

import UIKit

@IBDesignable
public class KTextField: UITextField {

    // MARK: - IBInspectable properties

    /// Applies border to the text view with the specified width
    @IBInspectable public var borderWidth: CGFloat = 0.0 {
        didSet {
            layer.borderWidth = borderWidth
            layer.borderColor = borderColor.cgColor
        }
    }

    /// Sets the color of the border
    @IBInspectable public var borderColor: UIColor = .clear {
        didSet {
            layer.borderColor = borderColor.cgColor
        }
    }

    /// Make the corners rounded with the specified radius
    @IBInspectable public var cornerRadius: CGFloat = 0.0 {
        didSet {
            layer.cornerRadius = cornerRadius
        }
    }

    /// Applies underline to the text view with the specified width
    @IBInspectable public var underLineWidth: CGFloat = 0.0 {
        didSet {
            updateUnderLineFrame()
        }
    }

    /// Sets the underline color
    @IBInspectable public var underLineColor: UIColor = .groupTableViewBackground {
        didSet {
            updateUnderLineUI()
        }
    }

    /// Sets the placeholder color
    @IBInspectable public var placeholderColor: UIColor = .lightGray {
        didSet {
            let placeholderStr = placeholder ?? ""
            attributedPlaceholder = NSAttributedString(string: placeholderStr, attributes: [NSForegroundColorAttributeName: placeholderColor])
        }
    }

    public override var placeholder: String? {
        didSet {
            let placeholderStr = placeholder ?? ""
            attributedPlaceholder = NSAttributedString(string: placeholderStr, attributes: [NSForegroundColorAttributeName: placeholderColor])
        }
    }

    /// Sets left margin
    @IBInspectable public var leftMargin: CGFloat = 10.0 {
        didSet {
            setMargins()
        }
    }

    /// Sets right margin
    @IBInspectable public var rightMargin: CGFloat = 10.0 {
        didSet {
            setMargins()
        }
    }

    // MARK: - init methods
    override public init(frame: CGRect) {
        super.init(frame: frame)
        applyStyles()
    }

    required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        applyStyles()
    }

    // MARK: - Layout
    override public func layoutSubviews() {
        super.layoutSubviews()
        updateUnderLineFrame()
        updateAccessoryViewFrame()
    }

    // MARK: - Styles
    private func applyStyles() {
        applyUnderLine()
        setMargins()
    }

    // MARK: - Underline
    private var underLineLayer = CALayer()
    private func applyUnderLine() {
        // Apply underline only if the text view's has no borders
        if borderStyle == UITextBorderStyle.none {
            underLineLayer.removeFromSuperlayer()
            updateUnderLineFrame()
            updateUnderLineUI()
            layer.addSublayer(underLineLayer)
            layer.masksToBounds = true
        }
    }

    private func updateUnderLineFrame() {
        var rect = bounds
        rect.origin.y = bounds.height - underLineWidth
        rect.size.height = underLineWidth
        underLineLayer.frame = rect
    }

    private func updateUnderLineUI() {
        underLineLayer.backgroundColor = underLineColor.cgColor
    }

    // MARK: - Margins
    private var leftAcessoryView = UIView()
    private var rightAcessoryView = UIView()
    private func setMargins() {
        // Left Margin
        leftView = nil
        leftViewMode = .never
        if leftMargin > 0 {
            if nil == leftView {
                leftAcessoryView.backgroundColor = .clear
                leftView = leftAcessoryView
                leftViewMode = .always
            }
        }
        updateAccessoryViewFrame()

        // Right Margin
        rightView = nil
        rightViewMode = .never
        if rightMargin > 0 {
            if nil == rightView {
                rightAcessoryView.backgroundColor = .clear
                rightView = rightAcessoryView
                rightViewMode = .always
            }
            updateAccessoryViewFrame()
        }
    }

    private func updateAccessoryViewFrame() {
        // Left View Frame
        var leftRect = bounds
        leftRect.size.width = leftMargin
        leftAcessoryView.frame = leftRect
        // Right View Frame
        var rightRect = bounds
        rightRect.size.width = rightMargin
        rightAcessoryView.frame = rightRect
    }

}