4 Ekim 2023

What is guard let in Swift?

141 1 ay önce

The "guard let" statement in Swift is used to safely unwrap an optional value and make sure it has a non-nil value within a specific scope. It's primarily used for early exits or error handling in a function or method when dealing with optional values.

That is sample usage of guard let.

guard let unwrappedValue = optionalValue else {
// Code to execute if optionalValue is nil
// This block must contain a return, throw, continue, or break statement

Here's what the different parts of the guard let statement mean:

unwrappedValue: This is the new non-optional variable that will hold the unwrapped value if optionalValue is not nil. It can be used within the scope following the guard let statement.

optionalValue: This is the optional value that you want to unwrap and use. If optionalValue is nil, the code block following the else keyword will be executed.

else: The keyword else is used to define the code block that should be executed if the optional value is nil. This block must contain a control transfer statement, such as return, throw, continue, or break, to exit the current scope. This is what ensures that the rest of the code in the function is not executed if the optional value is nil.

The main purpose of guard let is to improve code readability and maintainability by reducing the need for nested if let or if statements when working with optional values. It allows you to handle the case where the value is missing early in your function or method and then continue with the rest of your code in a more confident manner, knowing that the unwrapped value is not nil.

And now we conclude with an example:

func processItems(_ items: [Int?]) {
for item in items {
guard let unwrappedItem = item else {
print("Skipping nil item.")
print("Processing item: \(unwrappedItem)")

let itemList: [Int?] = [10, nil, 20, nil, 30]