Types in Swift

Swift’s type system is strict and expressive—numeric types, strings, booleans, and custom structs/enums all participate in compile-time checking with type inference.

Basic types

• Int, Double, Float, Bool — numbers and logic
• String — Unicode text (value semantics with copy-on-write optimization)
• Character — single extended grapheme cluster
• Integer sizes: Int8, UInt, etc., when you need explicit width

Type safety

let a: Int = 10
let b: Double = 10.0
// let sum = a + b  // compile error — must convert explicitly

Unlike JavaScript, Swift will not silently coerce incompatible numeric types.

Important interview questions and answers

1. Q: Int vs Int32?
   A: Int matches the platform word size (64-bit on modern Apple devices); use sized integers for binary protocols and interop.
2. Q: Is Swift dynamically typed?
   A: No—types are checked at compile time, with inference reducing annotation noise.

Self-check

1. Can you add Int and Double without conversion?
2. What type does true have?

Tip: Swift will not silently add Int and Double—convert explicitly like in strict typed languages.