A guard statement is basically a reverse if statement

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guard textField.text! != “” else { exit(1) } //If the condition is true, the program will continue. Kind of like a safe “assert()”

//Guard statements can also be used to unwrap optionals
guard let entry = someEntryField.entry else { presentWarning(“You have not entered anything”); return }

Why do these even exist?

First of all, they make your code prettier. They can flatten some code structures like pyramids of validation. It takes less effort to read “guard” and know what it means instead of “if !() {}”. Secondly, it introduces a method of unwrapping an optional and placing it in the active scope, instead of inside a body like an “if let” statement.

Originally published 04/15/2021 https://pittcsc.org/, republished 09/08/2022.