Swift·Swift from optionals to SwiftUI

Optionals

Use optional binding, nil coalescing and guard to handle absence.

Beginner 13 min read Lesson 2 of 300 Challenge included

What you will be able to do

Declare optional types with ?.
Use if let or guard let to unwrap.
Use ?? for defaults.
Avoid ! in production code.

In plain English

An optional either has a value or is nil. if let and guard let unwrap safely; ?? supplies a default. Avoid force unwrapping with ! unless the value is guaranteed by the API.

Optionals.swiftSwift

func greet(_ name: String?) -> String {
    guard let name, !name.isEmpty else { return "Hello, friend" }
    return "Hello, \(name)"
}

print(greet(nil))
print(greet("Ada"))

Your turn

Default an optional

Easy

Use ?? to default a nullable name to "friend".

SWIFT · starter

let safe =

Check your understanding before moving on.

Knowledge checkQuestion 1

Which operator provides a default for nil?

Select an answer to continue

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