Swift conditionals: the if statement

By Flavio Copes

Learn how to use if and else conditionals in Swift, write boolean conditions cleanly, and why Swift prevents the bug of assigning instead of comparing.

This tutorial belongs to the Swift series

if statements are the most popular way to perform a conditional check. We use the if keyword followed by a boolean expression, followed by a block containing code that is ran if the condition is true:

let condition = true
if condition == true {
    // code executed if the condition is true
}

An else block is executed if the condition is false:

let condition = true
if condition == true {
    // code executed if the condition is true
} else {
    // code executed if the condition is false
}

You can optionally wrap the condition validation into parentheses if you prefer:

if (condition == true) {
    // ...
}

And you can also just write:

if condition {
    // runs if `condition` is `true`
}

or

if !condition {
    // runs if `condition` is `false`
}

One thing that separates Swift from many other languages is that it prevents bugs caused by erroneously doing an assignment instead of a comparison. This means you can’t do this:

if condition = true {
    // The program does not compile
}

and the reason is that the assignment operator does not return anything, but the if conditional must be a boolean expression.

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