/// <summary>
/// Prompts the user for a valid value. Will continue to re-prompt until one is entered.
/// </summary>
/// <typeparam name="T">The type of value to be input. Supports structs.</typeparam>
/// <param name="prompt">The prompt displayed to the user</param>
/// <param name="defaultVal">The default value returned if no input is entered</param>
/// <param name="defaultValLabel">If a defaultVal is supplied, this label will be used instead of the value in the prompt. (e.g. you may wish to display TODAY instead of the full date)</param>
/// <param name="validator">Runs after the type conversion has taken place. If the function returns a string it will be displayed and the user will be reprompted for a valid value. </param>
/// <param name="converter">Overrides the converter supplied by the converterFactory (which defaults to TypeDescriptor.GetConverter unless overriden in constructor)</param>
/// <returns>A valid value in the specified type converted from user input.</returns>
public T For <T>(string prompt, T?defaultVal = null, string defaultValLabel = null, Func <T, string> validator = null, IConverter <T> converter = null) where T : struct
{
T result = default(T);
if (converter == null)
{
converter = _converterFactory.GetConverter <T>();
}
if (!converter.CanConvertFrom(typeof(string)))
{
throw new NotSupportedException(String.Format("{0} cannot convert from string to {1}", converter.GetType().ToString(), typeof(T).ToString()));
}
bool validInput = false;
do
{
string promptLine = !defaultVal.HasValue ? String.Format("{0}: ", prompt) : String.Format("{0} (ENTER for {1}): ", prompt, (!String.IsNullOrWhiteSpace(defaultValLabel) ? defaultValLabel : String.Format("\"{0}\"", defaultVal.ToString())));
_console.WriteLine(promptLine);
_console.WriteLine();
_console.Write("> ");
var userInput = _console.ReadLine();
// Return the default value if supplied and user hit ENTER
if (defaultVal.HasValue && String.IsNullOrWhiteSpace(userInput))
{
return(defaultVal.Value);
}
bool convertSuccess = false;
if (String.IsNullOrWhiteSpace(userInput))
{
_console.WriteLine("Please enter a value.");
}
else
{
// Otherwise try to convert the string to the specified type
try
{
result = converter.ConvertFromString(userInput);
convertSuccess = true;
}
catch
{
_console.WriteLine("Invalid input. Cannot convert \"{0}\" to {1}.", userInput, result.GetType().ToString());
}
}
if (convertSuccess)
{
if (validator == null)
{
validInput = true;
}
else
{
var validatorMessage = validator(result);
if (String.IsNullOrWhiteSpace(validatorMessage))
{
validInput = true;
}
else
{
_console.WriteLine(validatorMessage);
}
}
}
} while (!validInput);
return(result);
}