Coding for All
Lesson 9: Else
Else Do one thing when true, another when false.
1let isRaining = false
2if isRaining {
3 print("Take an umbrella!")
4} else {
5 print("Enjoy the sunshine!")
6}
Terminal
$ swift main.swift
Enjoy the sunshine!
Every line, explained
let isRaining = false
let creates a constant: a named box whose value is set once and can never change. Swift people reach for let by default: if a value never needs to change, locking it down prevents accidents.
if isRaining {
if checks a condition. Swift style: no round brackets around the condition, but the curly braces { } are always required. The condition is just the constant isRaining, which is false, so this block is skipped.
print("Take an umbrella!")
print(...) shows whatever is inside its round brackets in the terminal, then moves to a new line. All lowercase, both brackets needed, and no semicolon at the end; Swift doesn't use them. Skipped: the condition above is false.
} else {
} else { attaches an "otherwise" branch. When the if condition is false, the code inside the else block runs instead. Exactly one of the two blocks runs, never both.
print("Enjoy the sunshine!")
print(...) shows whatever is inside its round brackets in the terminal, then moves to a new line. All lowercase, both brackets needed, and no semicolon at the end; Swift doesn't use them. This is the line that runs.
}
This } closes the else block.