junioriOS
What are variables in Swift (let vs var)?
Updated May 6, 2026
Short answer
let defines constants and var defines mutable variables.
Deep explanation
let is used when value should not change after assignment, improving safety. var allows reassignment. Swift encourages immutability by default to reduce bugs.
Real-world example
Use let for API base URLs and var for changing UI states like loading indicators.
Common mistakes
- Using `var` everywhere instead of preferring `let`.
Follow-up questions
- Why does Swift prefer immutability?
- Can a let constant hold a mutable object?