Data Types

Swift is a strongly-typed language.

Basic Data Types:

Swift provides a rather large number of types. However, you can write perfectly good programs using only four of those:

Basic Swift Data Types

Here are some examples of declaring and initializing variables:

var age: Int = 28

var price: Double = 8.99

var message: String = "Game Over"

var lateToWork: Bool = true

Naming Constants and Variables:

Constant and variable names can contain almost any character, including Unicode characters:

let π = 3.14159
let 你好 = "你好世界"
let 🙂 = "happy"

Constant and variable names can’t contain whitespace characters, mathematical symbols, arrows, private-use Unicode scalar values, or line- and box-drawing characters. Nor can they begin with a number, although numbers may be included elsewhere within the name.

Numeric Type Conversion:

A type cast is basically a conversion from one type to another.

The notation (Type)value means “convert value to Type“. So for example:

double weight1;
int weight2;

weight1 = 154.49;
weight2 = (int) weight1;

// weight2 is now 154

Note: Going from a double to an int simply removes the decimal. There’s no rounding involved.