Swift Programming: The Big Nerd Ranch Guide

Exiting Early from a Function

You learned about Swift’s conditional statements in Chapter 3, but there is one more to introduce: guard statements. Just like if/else statements, guard statements execute code depending on a Boolean value resulting from some expression. But guard statements are different from what you have seen before. A guard statement is used to exit early from a function if some condition is not met. As their name suggests, you can think of guard statements as a way to protect your code from running under improper conditions.

Following the example above, consider an example in which you want to write a function that greets a person by their middle name if they have one. If they do not have a middle name, you would ...