[Solved] In Swift, what does the exclamation mark (!) after a variable type indicate?var username: String! — Ans: An implicitly unwrapped Optional | iOS Swift

iOS Swift - Swift Language Essentials

In Swift, what does the exclamation mark (!) after a variable type indicate?
var username: String!

AA forced cast to another type

BA non-optional variable

CA constant value

DAn implicitly unwrapped Optional

Step-by-Step Solution

Solution:

Step 1: Understand the syntax
The exclamation mark (!) after a type in Swift declares an implicitly unwrapped Optional, which means it can hold a value or nil but is automatically unwrapped when accessed.
Step 2: Differentiate from other options
It is not a non-optional (B), constant (C), or a forced cast (D).
Final Answer:
An implicitly unwrapped Optional -> Option D
Quick Check:
Exclamation mark after type means implicitly unwrapped Optional [OK]

Quick Trick: Exclamation mark after type means implicitly unwrapped Optional [OK]

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