Conditionals take an expression, which is code that evaluates to determine a value, and checks if it is true or false. If it’s true, we can tell our program to do one thing — we can even account for false to do another.

As we write more complex programs, conditionals allow us to address multiple scenarios and make our programs more robust.

if Statement

An if statement executes a code block when its condition evaluates to true. If the condition is false, the code block does not execute.

var halloween = true
if halloween {
print("Trick or treat!")
// Output: Trick or treat!

else if Statement

An else if statement provides additional conditions to check for within a standard if/else statement. else if statements can be chained and exist only after an if statement and before an else.

var weather = "rainy"
if weather == "sunny" {
print("Grab some sunscreen")
} else if weather == "rainy" {
print("Grab an umbrella")
} else if weather == "snowing" {
print("Wear your snow boots")
} else {
print("Invalid weather")
// Output: Grab an umbrella

else Statement

An else statement is an optional partner to an if statement. When the condition for the if statement evaluates to false, the code within the body of the else will execute.

var turbulence = false
if turbulence {
print("Please stay seated.")
} else {
print("You may freely move around.")
// Output: You may freely move around.
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