Working with Switch Statements

1. Video Overview

2. Introduction to Switch Statements

This tutorial has been verified using Unity 2019.4.11f1 LTS

In the same family as if and else, switch is a conditional statement. Just as a railroad switch guides a train to one of a number of possible tracks, a switch statement routes the flow of code to one of a number of possible code blocks. Where if statements are useful for true/false testing, switch statements are more efficient when testing the value held by a variable, or returned by an expression evaluation, against a set of expected cases. Similar to the optional else block that follows an if statement, a switch may execute a default block of code when no specified condition has been met.

It is important to note that switch statements are only able to test integers (not floating point numbers), characters, strings, Booleans, enumerations, and nullable data types.

Following are examples of three of the many uses of switch.

3. Example 1

In this example, we will use a switch statement to check whether a chosen option is a primary color, according to conventional color theory (Figure 01).

Figure 01: We’re only concerned with what’s on the primary list, so anything not on that list can be handled by the default code block.

Technical Steps:

1. In the Project window, right-click and select Create > C# Script.

2. For this example, name the script “ColorChecker”.

3. Double-click the script to open it in Visual Studio.

4. Delete the Start() section, as we won't be using that method for this exercise.

5. In this step, we define a new enum, a data type that lets us define members of a set, called “ColorChoice”. An enum must be defined before it can be declared as a data member type. For more information on enum, see Enumerations.

Beginning on line 7, type:

6. Now that we have defined ColorChoice, we can use it as a data type as we would int or bool.

Beginning on line 16, type:

7. In Update, beginning on line 21, type:

8. Save your script. It is now complete, and ready to be attached to a GameObject (Figure 02).

Figure 02: The completed ColorChecker script

9. Back in the Unity Editor, from the GameObject dropdown, select Create Empty GameObject. A new GameObject will appear in the hierarchy window. It’s good to name your objects so that their role in the Scene is clear. In the hierarchy window, right-click the newly created GameObject, select Rename, and type “ColorCheck”.

10. With ColorCheck selected, select the Add Component button below the Transform section in the Inspector.

11. Type Color Checker into the search bar. As you type, your options will narrow to those components whose name contains your search term(s). Select Color Checker in the list.

12. With ColorCheck still highlighted in the hierarchy, select the lock in the upper right-hand corner of the Unity Editor window, above the Inspector, to keep focus on our object.

13. In the upper center of the Unity Editor, select the Play button.

14. Direct your attention to the section of the Inspector named Color Checker (Script) (Figure 03).

Figure 03: By default, the first option in an enumeration is selected. In this case, the default is Red, a primary color, so the checkbox labeled Is A Primary Color is checked.

15. Selecting the dropdown labeled The Color, select the various colors and note the behavior of the checkbox. Even though we only specified code for three cases, all others can be handled by the default case.

16. Select Play again to end the demonstration.

4. Example 2

In this example, we will use switch to modify settings and behaviors of the game controller based on the current game mode. The sequence of an enum’s elements — the order in which you test for cases in a switch — is entirely up to you. You’re not required to match these sequences, but it will make your code easier to read and debug if you do. For this example, we’ll match both to the illustration (Figure 04).

Figure 04: Since we know there are only three possible game modes, and we want to handle them all individually, we won’t need a default code block for this switch.

Technical Steps:

1. In the project window, right-click and select Create > C# Script.

2. For this example, name the script “GameController”.

3. Double-click the script to open it in Visual Studio.

4. Delete the Start() section, as we won't be using that method for this exercise.

5. Beginning on line 7, type:

6. Beginning on line 13, type:

7. In Update(), beginning on line 22, type:

8. Save your script. It is now complete, and ready to be attached to a GameObject (Figure 05).

Figure 05: The completed GameController script

9. Back in the Unity Editor, from the GameObject dropdown, select Create Empty GameObject. A new GameObject will appear in the hierarchy window. It’s good to name your objects so that their role in the scene is clear. In the hierarchy window, right-click the newly created GameObject, select Rename, and type “GameControl”.

10. With GameControl selected, select the Add Component button below the Transform section in the Inspector.

11. Type “Game Controller” into the search bar. As you type, your options will narrow to those components whose name contains your search term(s). Select Game Controller in the list.

12. With GameControl still highlighted in the hierarchy, enable the lock in the upper right-hand corner of the Unity Editor, above the Inspector, to keep focus on our object.

13. In the upper center of the Unity Editor, select the Play button.

14. Note that Game Controller (Script), Paused is currently selected and its settings applied (Figure 06).

Figure 06: Game Controller (Script) is selected and set to Paused

15. Selecting the dropdown labeled Game Mode, select the various modes and note the changes in the game’s settings.

16. Select Play again to end the demonstration.

5. Example 3

In this example we will use both if and switch, among other commands, to create a simple game where you must guess a number chosen by the computer (Figure 07).

Figure 07: Because we first check to see if the secret number has been guessed, we know if we get to the switch that it hasn’t. This only leaves two possible cases: the guessed number is either too high or too low, so a default code block isn’t necessary.

Technical Steps:

1. In the project window, right-click and select Create > C# Script.

2. For this example, name the script “GuessingGame”.

3. Double-click the script to open it in Visual Studio.

4. While you’re not required to separate your private and public data members, doing so aids readability and provides a clear place for any necessary additional data members.

Beginning on line 7, type:

5. Because the maximum is exclusive in the integer version of Random.Range, we add 1 to make our chosen maximum (20 by default) possible.

In Start(), on line 16, type:

6. Before we invoke switch, we use if to check if the secret number has been guessed.

In Update(), beginning on line 22, type:

7. If we get to the switch, we know that the player has guessed incorrectly. Finding the sign of the difference between the guessed and secret numbers will tell us whether the guess was too high or low. Because Sign returns a float, and switch cannot evaluate those, we typecast to an int. For more information, see Mathf.Sign and Casting and Type Conversions.

Beginning on line 26, type:

8. Save your script. It is now complete and ready to be attached to a GameObject (Figure 08).

Figure 08: The completed GuessingGame script

9. Back in the Unity Editor, from the GameObject drop-down, select Create Empty GameObject. A new GameObject will appear in the hierarchy window. It’s good to name your objects so that their role in the Scene is clear. In the hierarchy window, right-click the newly created GameObject, select Rename, and type “NumberGuess”.

10. With NumberGuess selected, select the Add Component button below the Transform section in the Inspector.

11. Type “Guessing Game” into the search bar. As you type, your options will narrow to those components whose name contains your search term(s). Select Guessing Game in the list.

12. With NumberGuess still highlighted in the hierarchy, enable the lock in the upper right-hand corner of the Unity Editor, above the Inspector, to keep focus on our object.

13. In the upper center of the Unity Editor, select the Play button.

14. Direct your attention to the section of the Inspector named Guessing Game (Script) (Figure 09).

Figure 09: The Guessing Game (Script) section of the Inspector

15. Guess a whole number between 1 and the max number (inclusive) and type it into the input field labeled Your Guess. The field labeled Result will tell you if your guess was correct, too high, or too low. Keep guessing until you get it. A helpful strategy is to always guess nearest the center between the known possible minimum and maximum values.

16. Select Play again to end the demonstration. Try changing the max number, while not in Play mode, and selecting Play again. A new secret number is chosen each time Play mode is activated.

6. Conclusion

This has been just a sampling of what switch is capable of. It is a versatile, simple command that can be used as a cleaner alternative to an if-else if-else if-...-else sequence, all the way to implementing finite state machines.