LoggerTextView is a subclass of UITextView that can be used as a log for QA of a project. Uses https://gist.github.com/popmedic/291af6918ac4f0a43d187e2379484c64

Logger.swift

import UIKit

let __kDefaultColorError = UIColor.redColor()
let __kDefaultColorSuccess = UIColor.greenColor()
let __kDefaultColor = UIColor.whiteColor()
let __kDefaultColorBackground = UIColor.blackColor()

let __kDefaultFont = UIFont(name: "Menlo-Bold", size: 12.0)!

let __kLoggerTextFieldListenerName = "com.webroot.control.LoggerTextField"

public class Logger {
    /// Singleton for logging
    public static var shared:Logger = Logger()
    /// UIColor to use for logError
    public var errorColor = __kDefaultColorError
    /// UIColor to use for logSuccess
    public var successColor = __kDefaultColorSuccess
    
    /// Private Array of classes that will listen to the logger for events
    public var _listeners = [(name:String,listener:LoggerListener)]()
    /// Private Array of AttributedStrings, stores all the lines logged (a line is added every time a log function is called.
    private var _lines = [NSAttributedString]()
    /// Private UIColor used to override the super.textColor values.
    private var _color = __kDefaultColor
    /// Private UIColor used to override the super.backgroundColor values.
    private var _backgroundColor = __kDefaultColorBackground
    /// Private UIFont used to override the super.font values.
    private var _font = __kDefaultFont
    /// clear - Clears the text.
    public func clear(){
        self._lines.removeAll()
    }
    /// refresh - Refreshes the text
    public func refresh(){
        let oldLines = self._lines
        self.clear()
        for line in oldLines {
            self.log(Attributed:line, logToDBGLog: false)
        }
    }
    /// addListener - Adds a LoggerListener with name name
    public func addListener(listener:LoggerListener, name: String) {
        self._listeners.append((name:name, listener:listener))
    }
    /// removeListener - Removes a LoggerListener with name name
    public func removeListener(name:String) {
        for (index, value) in self._listeners.enumerate() {
            if value.name == name {
                self._listeners.removeAtIndex(index)
            }
        }
    }
    /**
     log - log a message to the view.
     
     - Note: This function will advance and add a endline to the string.  Formatting is only on the current string.
     - Parameters:
     - message: string to be logged
     - color: forground color for message
     - backgroundColor: background color for message (to end of string NOT end of line).
     - font: font to use for the message
     */
    public func log(message:String, color:UIColor = __kDefaultColor, backgroundColor:UIColor = __kDefaultColorBackground, font:UIFont = __kDefaultFont) {
        self.log(Attributed:NSAttributedString(string: message, attributes: [
            NSFontAttributeName:font,
            NSForegroundColorAttributeName:color,
            NSBackgroundColorAttributeName:backgroundColor
            ]))
        
    }
    /**
     log - Adds a message.
     
     - Note: This function will advance and add a endline to the string.  Formatting is only on the current string NOT the line.
     - Parameters:
     - Attributed attributedMessage: NSAttributedString to be logged
     - logToDBGLog: Bool, when true will call NSLog (or equevilent)
     */
    public func log(Attributed attributedMessage:NSAttributedString, logToDBGLog:Bool = true){
        self._lines.append(attributedMessage)
        for value in self._listeners {
            value.listener.loggedLine(attributedMessage)
        }
        if logToDBGLog {
            Logger.xcdbgFriendly(attributedMessage.string)
        }
    }
    /**
     logSuccess - log a message to the view using the successColor UIColor for textColor/tintColor.
     
     - Note - This function will advance add and an endline to the string.  Formatting is only on the current string.
     - Parameters:
     - message: string to be logged
     */
    public func logSuccess(message:String) {
        self.log(message, color: self.successColor)
    }
    /**
     logError - log a message to the view using the errorColor UIColor for textColor/tintColor.
     
     - Note - This function will advance add and an endline to the string.  Formatting is only on the current string.
     - Parameters:
     - message: string to be logged
     */
    public func logError(message:String) {
        self.log(message, color: self.errorColor)
    }
    /**
     xclog - This function will log to the NSLog regardless of it being a debug configuration.
     
     - Parameters:
        - object: object to log to log.
        - filename: (optional, default to current file name) file to add to the string as where the log function was called from
        - line: (optional, defaults to current line) line in filename that the log function was called from
        - funcname: (optional, defaults to current function) name of function at line of filename that the log function was called from
    */
    public static func xclog<T>(object: T, filename: String = #file, line: Int = #line, funcname: String = #function) {
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "MM/dd/yyyy HH:mm:ss:SSS"
        let process = NSProcessInfo.processInfo()
        var threadId = "\(NSThread.currentThread())"
        threadId = threadId.substringWithRange(threadId.startIndex.advancedBy(13)..<threadId.startIndex.advancedBy(22)) //.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString: "<")).stringByReplacingOccurrencesOfString("NSThread: 0x", withString: "")
        print("\(dateFormatter.stringFromDate(NSDate())) \(process.processName)[\(process.processIdentifier):\(threadId)] \((filename as NSString).lastPathComponent)(\(line)) \(funcname):\r\(object)")
    }
    public static func xclogFriendly<T>(object:T) {
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "MM/dd/yyyy HH:mm:ss:SSS"
        let process = NSProcessInfo.processInfo()
        var threadId = "\(NSThread.currentThread())"
        threadId = threadId.substringWithRange(threadId.startIndex.advancedBy(13)..<threadId.startIndex.advancedBy(22)) //.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString: "<")).stringByReplacingOccurrencesOfString("NSThread: 0x", withString: "")
        print("\(dateFormatter.stringFromDate(NSDate())) \(process.processName)[\(process.processIdentifier):\(threadId)] \(object)")
    }
    /**
     dbg - This function will log to the NSLog only if it is a debug configuration.
     
     - Parameters:
     - object: object to log to log.
     - filename: (optional, default to current file name) file to add to the string as where the log function was called from
     - line: (optional, defaults to current line) line in filename that the log function was called from
     - funcname: (optional, defaults to current function) name of function at line of filename that the log function was called from
     */
    public static func xcdbg<T>(object: T, filename: String = #file, line: Int = #line, funcname: String = #function){
        #if DEBUG
            xclog(object, filename: filename, line: line, funcname: funcname)
        #else
        #endif
    }
    public static func xcdbgFriendly<T>(object: T){
        #if DEBUG
            xclogFriendly(object)
        #else
        #endif
    }
}

public protocol LoggerListener {
    func loggedLine(line:NSAttributedString)
}

public class LoggerTextView: UITextView, LoggerListener {
    /// UIColor to use for logError
    public var errorColor = __kDefaultColorError
    /// UIColor to use for logSuccess
    public var successColor = __kDefaultColorSuccess
    /// Bool: when true every log has a line number (NOTE: based on logs NOT newlines/charage returns.)
    public var showLineNumbers:Bool {
        get{
            return _showLineNumbers
        }
        set(value) {
            if value != _showLineNumbers {
                _showLineNumbers = value
                refresh()
            }
        }
    }
    
    /// Private UIColor used to override the super.textColor values.
    private var _color = __kDefaultColor
    /// Private UIColor used to override the super.backgroundColor values.
    private var _backgroundColor = __kDefaultColorBackground
    /// Private UIFont used to override the super.font values.
    private var _font = __kDefaultFont
    /// Private Bool used for the showLineNumbers property.
    private var _showLineNumbers = false
    /// Public UIColor property for the default background color.
    override public var backgroundColor: UIColor? {
        get {
            return self._backgroundColor
        }
        set(value) {
            if let val = value {
                self._backgroundColor = val
            }
        }
    }
    /// Public UIColor property for the default textColor color.
    override public var textColor: UIColor? {
        get {
            return self._color
        }
        set(value) {
            if let val = value {
                self._color = val
            }
        }
    }
    /// Public UIColor property for the default tintColor color.
    override public var tintColor: UIColor? {
        get {
            return self._color
        }
        set(value) {
            if let val = value {
                self._color = val
            }
        }
    }
    /// Public UIFont property for the default font font.
    override public var font: UIFont? {
        get {
            return self._font
        }
        set(value) {
            if let val = value {
                self._font = val
            }
        }
    }
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        self._initialize()
    }
    
    required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self._initialize()
    }
    /// Private function for common initialization
    private func _initialize(){
        self.editable = false
        self.selectable = true
        self.scrollEnabled = true
        
        if self.font == nil {
            self.font = __kDefaultFont
        }
        if self.backgroundColor == nil {
            self.backgroundColor = __kDefaultColorBackground
        }
        if self.textColor == nil {
            self.textColor = __kDefaultColor
        }
        if self.tintColor == nil {
            self.tintColor = __kDefaultColor
        }
        
        Logger.shared.addListener(self, name: __kLoggerTextFieldListenerName)
    }
    /// clear - Clears the text.
    public func clear(){
        self.text = ""
        Logger.shared.clear()
    }
    /// refresh - Refreshes the text
    public func refresh(){
        let oldLines = Logger.shared._lines
        self.clear()
        for line in oldLines {
            self.log(Attributed:line, logToDBGLog: false)
        }
    }
    /**
        log - log a message to the view.
    
        - Note: This function will advance and add a endline to the string.  Formatting is only on the current string.
        - Parameters:
            - message: string to be logged
            - color: forground color for message
            - backgroundColor: background color for message (to end of string NOT end of line).
            - font: font to use for the message
    */
    public func log(message:String, color:UIColor, backgroundColor:UIColor, font:UIFont) {
        self.log(Attributed:NSAttributedString(string: message, attributes: [
            NSFontAttributeName:font,
            NSForegroundColorAttributeName:color,
            NSBackgroundColorAttributeName:backgroundColor
            ]))
        
    }
    /**
         log - log a message to the view.
         
         - Note: This function will advance and add a endline to the string.  Formatting is only on the current string NOT the line.
         - Parameters:
            - Attributed attributedMessage: NSAttributedString to be logged
            - logToDBGLog: Bool when true will print to xcode log.
     */
    public func log(Attributed attributedMessage:NSAttributedString, logToDBGLog:Bool = true){
        Logger.shared.log(Attributed: attributedMessage, logToDBGLog: logToDBGLog)
    }
    /**
         log - log a message to the view.
         
         - Note: This function will advance add and an endline to the string.  Formatting is only on the current string.
         - Parameters:
             - message: string to be logged
     */
    public func log(message:String) {
        if let color = self.textColor {
            self.log(message, color: color)
        }
        else {
            self.log(message, color: __kDefaultColor)
        }
    }
    /**
         log - log a message to the view.
         
         - Note: This function will advance add and an endline to the string.  Formatting is only on the current string.
         - Parameters:
             - message: string to be logged
             - color: forground color for message
     */
    public func log(message:String, color:UIColor) {
        if let backgroundColor = self.backgroundColor {
            self.log(message, color: color, backgroundColor: backgroundColor)
        }
        else {
            self.log(message, color: color, backgroundColor:__kDefaultColorBackground)
        }
    }
    /**
         log - log a message to the view.
         
        - Note: This function will advance add and an endline to the string.  Formatting is only on the current string.
        
        - Parameters:
             - message: string to be logged
             - color: forground color for message
             - backgroundColor: background color for message (to end of string NOT end of line).
     */
    public func log(message:String, color:UIColor, backgroundColor:UIColor) {
        if let font = self.font {
            self.log(message, color: color, backgroundColor: backgroundColor, font: font)
        }
        else {
            self.log(message, color: color, backgroundColor: backgroundColor, font: __kDefaultFont)
        }
    }
    /**
         logSuccess - log a message to the view using the successColor UIColor for textColor/tintColor.
         
         - Note - This function will advance add and an endline to the string.  Formatting is only on the current string.
         - Parameters:
             - message: string to be logged
     */
    public func logSuccess(message:String) {
        self.log(message, color: self.successColor)
    }
    /**
         logError - log a message to the view using the errorColor UIColor for textColor/tintColor.
         
         - Note - This function will advance add and an endline to the string.  Formatting is only on the current string.
         - Parameters:
             - message: string to be logged
     */
    public func logError(message:String) {
        self.log(message, color: self.errorColor)
    }
    public func loggedLine(line: NSAttributedString) {
        let mutableTextAttributedString = NSMutableAttributedString(attributedString: self.attributedText)
        if self.showLineNumbers {
            mutableTextAttributedString.appendAttributedString(NSAttributedString(string: "\(Logger.shared._lines.count):\t", attributes: [
                NSFontAttributeName:self._font,
                NSForegroundColorAttributeName:self._color,
                NSBackgroundColorAttributeName:self._backgroundColor
                ]))
        }
        mutableTextAttributedString.appendAttributedString(line)
        mutableTextAttributedString.appendAttributedString(NSAttributedString(string: "\n", attributes: [
            NSFontAttributeName:self._font,
            NSForegroundColorAttributeName:self._color,
            NSBackgroundColorAttributeName:self._backgroundColor
            ]))
        self.attributedText = mutableTextAttributedString
        self.scrollRangeToVisible(NSRange(location: self.attributedText.length-1, length: 1))
    }
}