21. Swift – Properties
Swift
Swift language provides properties for class, enumeration or structure to associate values. Properties can be further classified into Stored properties and Computed properties. Difference between Stored Properties and Computed Properties
Stored Property
Computed Property
Store constant and variable values as instance
Calculate a value rather than storing the value
Provided by classes and structures
Provided by classes, enumerations and structures
Both Stored and Computed properties are associated with instances type. When the properties are associated with its type values then it is defined as 'Type Properties'. Stored and computed properties are usually associated with instances of a particular type. However, properties can also be associated with the type itself. Such properties are known as type properties. Property observers are also used
To observe the value of the stored properties
To observe the property of inherited subclass derived from superclass
Stored Properties Swift introduces Stored Property concept to store the instances of constants and variables. Stored properties of constants are defined by the 'let' keyword and Stored properties of variables are defined by the 'var' keyword.
During definition Stored property provides 'default value'
During Initialization the user can initialize and modify the initial values
struct Number { var digits: Int let pi = 3.1415 }
var n = Number(digits: 12345) n.digits = 67 107