Comparing structs vs classes decision in Swift - Quick Revision & Key Differences

Recall & Review

beginner

What is a key difference between structs and classes in Swift regarding memory management?

Structs are value types, so they are copied when assigned or passed around. Classes are reference types, so they share a single instance in memory.

beginner

When should you choose a struct over a class in Swift?

Choose a struct when you want simple data containers that are copied on assignment, have no inheritance, and are thread-safe by default.

beginner

What feature do classes have that structs do not in Swift?

Classes support inheritance, allowing one class to inherit properties and methods from another. Structs do not support inheritance.

intermediate

How does mutability differ between structs and classes in Swift?

Structs require the 'mutating' keyword to change properties inside methods, and instances must be declared 'var' to be mutable. Classes allow property changes without 'mutating' and can be mutable even if declared with 'let'.

intermediate

Why might you prefer classes when working with shared, mutable state?

Because classes are reference types, multiple parts of your code can share and modify the same instance, which is useful for shared mutable state.

Which of the following is true about Swift structs?

A They support inheritance.

B They are copied when assigned to a new variable.

C They are reference types.

D They can be mutated even if declared with let.

Structs are value types, so they are copied on assignment. They do not support inheritance and cannot be mutated if declared with let.

What keyword is required to modify properties inside a struct method?

A mutating

B var

C change

D mutate

The 'mutating' keyword is required in struct methods that modify properties.

Why might you choose a class over a struct?

A You want value semantics.

B You want automatic copying.

C You need inheritance.

D You want thread safety by default.

Classes support inheritance, which structs do not.

If you want multiple parts of your app to share and modify the same data instance, which should you use?

A Class

B Struct

C Enum

D Tuple

Classes are reference types, so they allow shared mutable state.

Which statement about mutability is correct?

A Classes require mutating keyword for property changes.

B Class instances declared with let cannot have their properties changed.

C Struct instances declared with let can have their properties changed.

D Struct methods that modify properties must be marked mutating.

Only struct methods that modify properties need the 'mutating' keyword. Classes do not require it.

Explain when you would choose a struct versus a class in Swift and why.

Think about how data is shared or copied and if you need inheritance.

Describe the impact of using structs on thread safety compared to classes.

Consider how copying versus sharing affects concurrent access.