Swift MCQ Questions

i is an Int and 6.0 is a Double. Swift won't multiply different numeric types without conversion, so the code is invalid.

String interpolation always produces a String, so value1 is the String "4".

Iterating a dictionary gives (key, value) pairs, and print accepts several arguments, so nothing is wrong with the code.

Explicit type annotations specify types using colon syntax: var name: Type. Use when inference is unclear, you want a specific type different from the inferred one, or for clarity. Annotations are required for properties without initial values. Balancing inference and explicit annotations improves code clarity.

Xcode generates a header named after the module, so for module Example you import "Example-Swift.h".

append(4), insert(5, at: 1) and += [5] all add values to the var array, so all of these answers are correct.

In the bridging header, Objective-C headers are added with #import "CustomObject.h".

let (a, b, c, d) = rectangle decomposes the tuple into separate constants.

Swift enumerations are value types, like structures; they are copied when assigned.

The function's type is (Int, Int) -> Int.

Objective-C classes are made available to Swift through a bridging header.

A mutating method is a method of a struct or enum that modifies self (its properties). It must be marked with the mutating keyword.

The enum declares no raw type, so it has no raw value type.

A literal that mixes strings and integers can only be typed as [Any], and Swift requires that annotation to be written.

\(val) inside a string literal inserts the value of val: that is string interpolation.

The let keyword declares constants (immutable bindings) whose values cannot be reassigned after initialization, while var declares variables (mutable bindings) that can be changed. In let x = 10, x is immutable; in var x = 10, x can be reassigned. Swift encourages using let by default for safety and clarity. This distinction applies to the binding, not necessarily the referenced object's internal mutability for reference types.

Nothing is wrong: the literal 10 is inferred as a Double, so 5.0 + 10 gives 15.0. Only variables of different types can't be mixed.