2. Conditionals

Comparison operators

• Comparison operators are used to compare two variables
  • They return either true or false
• Two variables of any type can be compared with equality operators
  • Equal to: a == b
  • Not equal to: a != b
• Two numbers can be further compared with less/greater operators:
  • Less than: a < b
  • Less than or equal: a <= b
  • Greater than: a > b
  • Greater than or equal: a >= b

if, else if, and else

• Checks truthfulness of a given statement
• The statements are checked in order, and the first true condition is executed

float temperatureInOulu = 2.3f;
float temperatureInIvalo = -10.9f;

if (temperatureInOulu > temperatureInIvalo)
{
    Debug.Log("Oulu is warmer than Ivalo");
}
else if (temperatureInOulu < temperatureInIvalo)
{
    Debug.Log("Ivalo is warmer than Oulu");
}
else 
{
    Debug.Log("Oulu and Ivalo have the same temperature");
}

Exercise 1: Sauna temperature

Print one of the messages from this sauna thermometer according to value of variable temperatureInSauna:

Single statement if

• If you only have one statement inside the if statement, curly braces can be left out

  if (temperatureInOulu > temperatureInIvalo)
  {
      Debug.Log("Oulu is warmer than Ivalo");
  }
  

  is the same as

  if (temperatureInOulu > temperatureInIvalo)
      Debug.Log("Oulu is warmer than Ivalo");
  

• You can even write the statement and the block to the same line!

  if (baa > 20) Debug.Log("Baa");
  else Debug.Log("Not baa!");
  

Not operator !

bool itsColdOutside = true;

• ! in front of a boolean value flips it from true to false, and vice versa

  if (!itsColdOutside)
      Debug.Log("It's warm outside.");
  

  is the same as

    if (itsColdOutside == false)
      Debug.Log("It's warm outside.");
  

Assignment operators

• We have used the assignment operator = for assigning values for variables

  int x;
  x = 25;
  

• Notice the difference between = and the conditional ==!

  • = is used for assigning values for variables, == is used for comparing values

Assignment Shorthands

• these three examples do the same thing:
  • i = i + 1;
  • i += 1;
  • i++;
• works similarly for subtraction, multiplication, division, modulo

Logical operators

• The three important logical operators

  • not: !a
  • and: a && b
  • or: a || b

• They can be used for more complicated logic

  int a = 1;
  int b = 3;
  int c = 5;
  
  Debug.Log(a < b && a < c);  // prints true
  

Logical operator example

• So, instead of nesting if statements like this:

  if (PlayerHealth > 0)
    if (PressedJumpButton)
      PlayerJump();
  

• Use the && ("and") operator:

  if (PlayerHealth > 0 && PressedJumpButton)
    PlayerJump();
  

Extra conditional: Switch-case statement

public int intelligence = 5;

void Greet()
{
	switch (intelligence)
	{
	case 5:
		Debug.Log("Why hello there good sir! Let me teach you about Trigonometry!");
		break;
	case 4:
		Debug.Log("Hello and good day!");
		break;
	case 3:
		Debug.Log("Whadya want?");
		break;
	case 2:
		Debug.Log("Grog SMASH!");
		break;
	case 1:
		Debug.Log("Ulg, glib, Pblblblblb");
		break;
	default:
		Debug.Log("Incorrect intelligence level.");
		break;
	}
}

Extra conditional: Switch expression

• There's an even shorter way to create a switch statement nowadays - switch expression:

  string saunaMessage = temperatureInSauna switch
  {
      <= 20 => "Vilulla hyräättää",
      > 20 and <= 40 => "Väljhoosut poes",
      > 40 and <= 60 => "Eepä tule yskä",
      > 60 and <= 80 => "Saanassako myö ollaan?",
      > 80 and <= 100 => "*Insert vihta kuva here*",
      > 100 => "Ovi aaki ja justiisai"
  };
  Debug.Log(saunaMessage);
  

Extra conditional: Ternary operator

• "Inline if" is done with the ternary operator

  • (the if statement) ? (if true) : (if false);

    message = health > 0 ? "Player is Alive" : "Player is Dead";
    

Strings

• String is a variable containing block of text

  • (Actually, a special type of variable containing an array of characters)

  string name = "Matti Teppo";
  

• You can concatenate (combine) multiple strings with the + operator:

  string firstName = "Matti";
  string lastName = "Teppo";
  string fullName = firstName + " " + lastName;
  
  Debug.Log(fullName);    // Outputs "Matti Teppo"
  

Special characters

• Special character constants are preceded by a backslash \

  • Can be used for formatting strings
  • The most used one, \n represents a newline, a.k.a. a line break

  string firstName = "Matti";
  string lastName = "Teppo";
  string fullName = firstName + "\n" + lastName;
  
  Debug.Log(fullName);
  /* This outputs:
  Matti
  Teppo
  */
  

String interpolation

• Concatenating multiple variables into one string with + quickly becomes tedious

• It's much easier to use string interpolation

  • Start a string with $, enclose variables in { curly braces }

    string animal = "Dog";
    string sound = "Woof";
    Debug.Log($"{animal} says {sound}!");
    // Outputs "Dog says Woof!"
    

• Very useful e.g., for printing multiple variables in one log statement:

  Debug.Log($"variable 1: {variable1}, variable 2: {variable2}");
  

Exercise 2: GameObject check

Create a C# script that checks if the GameObject is

• a player or
• an enemy.

Give the GameObject a string variable EntityType that tells which of the two it is.

• Depending on its value,
  a) Set the HP value of the GameObject to 50 or 10.
  b) print to console either "I am Player! My HP is 50!" or "I am Enemy! My HP is 10!"

• What happens if
  a) EntityType is something else
  b) EntityType is not declared at all?