A variable in programming, so also in Swift, is a named value that can be changed during the execution of a program. There are many different types of variables in Swift, including:
- Int: used for whole numbers
- Double and Float: used for floating-point numbers
- String: used for storing text
- Bool: used for storing true/false values
- Array: used for storing multiple values of the same type in an ordered list
- Dictionary: used for storing key-value pairs
- Optional: used to represent the possible absence of a value of a certain type
Variables in Swift can be declared using the “var” keyword for mutable values or the “let” keyword for immutable values, speak constants.
Note that Swift is a strongly-typed language, so you must specify the type of a variable when you declare it. To declare a variable in Swift, you use the following syntax: var variableName: DataType = initialValue. For example, to declare a variable named `age` of type `Int` with an initial value of 20, you would write:
var age: Int = 20
Swift also supports type inference, which means that the compiler can automatically determine the data type of a variable based on its initial value. So you can also declare the above variable using type inference like this:
var age = 20
This is a shorthand way of declaring a variable that lets the Swift compiler infer the type of the variable based on the initial value.