如何避免多次重复类似的代码？

Question

I'm doing a Subway restaurant like console application. It's heavily dependent on loops, and there's a specific kind of loop I've repeated lots of times.

Basically, I write the options, then I make the cursor be over the initial option. Whatever option the user presses enter while the cursor is over it, is the selected option.

Here's the first part of the code (it's kinda big, but that's why I'm asking here after all):

static int Row = 0; //To set the row of the cursor

    static void Menu()
    {
        Console.WriteLine("Hi, welcome to Subway!"); //Line 0
        Console.WriteLine(); //Line 1

        //Bread Selection
        string[] breadOptions =
        {
                        "Hearty Italian",       //Element 0
                        "9-Grain Honey Oat",    //Element 1
                        "Jalapeno Cheese",      //Element 2
                        "Monterey Cheddar",     //Element 3
                        "Parmesan Oregano",     //Element 4
                        "Roasted Garlic",       //Element 5
                        "Rosemary & Sea Salt",  //Element 6
                        "Rye Bread",            //Element 7
                        "Gluten-Free Bread",    //Element 8
        };

        Console.WriteLine("Choose you bread!"); //Line 2
        Console.WriteLine("[ ]" + breadOptions[0]); //Line 3
        Console.WriteLine("[ ]" + breadOptions[1]); //Line 4
        Console.WriteLine("[ ]" + breadOptions[2]); //Line 5
        Console.WriteLine("[ ]" + breadOptions[3]); //Line 6
        Console.WriteLine("[ ]" + breadOptions[4]); //Line 7
        Console.WriteLine("[ ]" + breadOptions[5]); //Line 8
        Console.WriteLine("[ ]" + breadOptions[6]); //Line 9
        Console.WriteLine("[ ]" + breadOptions[7]); //Line 10
        Console.WriteLine("[ ]" + breadOptions[8]); //Line 11

        Row = 3; //set the row to the first bread option
        int currentBread = 0; //a couter to keep track of the bread
        ConsoleKeyInfo breadKey = new ConsoleKeyInfo();

        do
        {   //Loop that goes with the cursor through the menu items
            for (Row = 3; Row < breadOptions.Length + 3; Row++)
            {
                //Highlight the current bread with the cursor in the box
                if (currentBread == Row - 3)
                    Console.SetCursorPosition(1, Row);
            }

            //reads the key
            breadKey = Console.ReadKey();
            switch (breadKey.Key)
            {
                case ConsoleKey.DownArrow:
                    //if the current item is the last one in the array, reset the counter.
                    if (currentBread == breadOptions.Length - 1)
                        //-1 because currentBread follows the array, and array starts at 0
                        //but the array lengh doensn't start at 0. 0 is an empty array
                        currentBread = 0;
                    //otherwise, add one to the counter
                    else
                        currentBread++;
                    break;

                case ConsoleKey.UpArrow:
                    //if the user presses Up in the first option, it goes to the last
                    if (currentBread == 0)
                        currentBread = breadOptions.Length - 1;
                    //otherwise, remove one from the counter
                    else
                        currentBread--;
                    break;
            }

        }
        //keep looping until the user presses enter
        while (breadKey.Key != ConsoleKey.Enter);

        Console.SetCursorPosition(0, 12); //set the cursor back to the next line after the last Console.WriteLine

        //make a string to store the selected bread and make it be the selected bread
        string bread = breadOptions[currentBread];

And, this do-while loop is repeated again several times, here's another example:

//Bread Size
        string[] sizeOptions = { "6-inches", "Footlong"};

        Console.WriteLine(); //Line 12
        Console.WriteLine("Choose a bread size."); //Line 13
        Console.WriteLine("[ ]" + sizeOptions[0]); //Line 14
        Console.WriteLine("[ ]" + sizeOptions[1]); //Line 15

        Row = 14;
        int currentSize = 0;
        ConsoleKeyInfo sizeKey = new ConsoleKeyInfo();

        do
        {
            for (Row = 14; Row < sizeOptions.Length + 14; Row++)
            {
                if (currentSize == Row - 14)
                    Console.SetCursorPosition(1, Row);
            }

            sizeKey = Console.ReadKey();
            switch (sizeKey.Key)
            {
                case ConsoleKey.DownArrow:
                    if (currentSize == sizeOptions.Length - 1)
                        currentSize = 0;
                    else
                        currentSize++;
                    break;
                case ConsoleKey.UpArrow:
                    if (currentSize == 0)
                        currentSize = sizeOptions.Length - 1;
                    else
                        currentSize--;
                    break;
            }
        } while (sizeKey.Key != ConsoleKey.Enter);

        Console.SetCursorPosition(0, 16);

        string size = sizeOptions[currentSize];

I was wondering if there's a way to not write this loop every time I need to choose an option.

Answer 1

You can use a method to do this:

    int GetOption(int startRow, string[] options)
    {
        int currentOption = 0;
        ConsoleKeyInfo sizeKey = new ConsoleKeyInfo();

        do
        {
            for (int i = startRow; i < options.Length + startRow; i++)
            {
                if (currentOption == i - startRow)
                    Console.SetCursorPosition(1, i);
            }

            sizeKey = Console.ReadKey();
            switch (sizeKey.Key)
            {
                case ConsoleKey.DownArrow:
                    if (currentOption == options.Length - 1)
                        currentOption = 0;
                    else
                        currentOption++;
                    break;
                case ConsoleKey.UpArrow:
                    if (currentOption == 0)
                        currentOption = options.Length - 1;
                    else
                        currentOption--;
                    break;
            }
        } while (sizeKey.Key != ConsoleKey.Enter);

        return currentOption;
    }

Usage:

    string[] sizeOptions = { "6-inches", "Footlong"};
    Console.WriteLine(); //Line 12
    Console.WriteLine("Choose a bread size."); //Line 13
    Console.WriteLine("[ ]" + sizeOptions[0]); //Line 14
    Console.WriteLine("[ ]" + sizeOptions[1]); //Line 15

    Row = 14;
    int currentSize = GetOption(Row, sizeOptions);
    Console.SetCursorPosition(0, 16);
    string size = sizeOptions[currentSize];

I can't test it right now, but I hope it helps you!

Answer 2

Take one of the chunks of the code which you want to re-use and move it into a new method with no parameters. Like the bit where you write out the options.

Ask yourself what is in that method which the other scenario doesn't want to be like that. In the list of options scenario, the thing which varies from one place to another is the actual list of things. So we need to turn that thing into a variable (so named because the value can vary ). Specifically, if you make the list of things a parameter to the method, then you can call that method from each different place, passing the relevant list.

Note that by doing this, it can cause you other problems to overcome. For example, where you print the list, you are currently hard coding each index that you want to print, so you need to find a more flexible way of doing that - a way of listing all the items in a collection, regardless how many there are. Try looking up foreach as a way of doing this.

Moving code from one place to another to make it better is called refactoring, and is a really important skill to learn in software development. I have only shown one of the kinds of problems that occurs when refactoring, but it's a big topic. Hope this helps.