You want to create a protocol Vehicle with a property speed that can be read and set. Which of these protocol declarations is correct?

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iOS Swift - Swift Language Essentials

You want to create a protocol Vehicle with a property speed that can be read and set. Which of these protocol declarations is correct?

Aprotocol Vehicle { var speed: Int { get set } }

Bprotocol Vehicle { var speed: Int }

Cprotocol Vehicle { func speed() -> Int }

Dprotocol Vehicle { let speed: Int }

Step-by-Step Solution

Solution:

Step 1: Understand property requirements in protocols
To require a property to be readable and writable, use { get set } in the protocol.
Step 2: Analyze each option
protocol Vehicle { var speed: Int { get set } } correctly declares speed as a variable property with get set. protocol Vehicle { var speed: Int } misses get set, so it's read-only. protocol Vehicle { func speed() -> Int } declares a method, not a property. protocol Vehicle { let speed: Int } uses let, which is not allowed in protocols.
Final Answer:
protocol Vehicle { var speed: Int { get set } } -> Option A
Quick Check:
Writable property = var with get set [OK]

Quick Trick: Use 'var' with { get set } for read-write properties [OK]

Common Mistakes:

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