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This chapter covers complex structures: Tuple, Struct, Class.
They can be extended using: Protocol, Extensions.
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Tuple Data Type contains list of Parameters.
Variable can have named Parameters. When storing values using Parameter names order doesn't matter.
Tuples
//DECLARE & INITIALIZE TUPLE VARIABLE.
var error1 = (1, "RED") //Implicit data types.
var error2 : ( Int, String) = (1, "RED") //Explicit data types. Same order.
var error3 : (code: Int, message: String) = (1, "RED") //Named data types. Same order.
var error4 : (code: Int, message: String) = (message:"RED", code:1) //Named data types. Any order.
//DECLARE TUPLE VARIABLE. STORE DATA LATER.
var error : (code: Int, message: String) //Named data types. No nitialization.
error = (1, "RED")
error = (message:"RED", code:1) //Named data types. Any order.
error.0 = 1
error.code = 1
//REFERENCE TUPLE & ITS VALUES.
print(error) //(code: 1, message: "RED")
print(error.0) //1 Reference Parameter using index.
print(error.message) //RED Reference Parameter using name.
//EXTRACT TUPLE VALUES.
var (myCode, myMessage) = error //Store Tuple Parameters into Variables. Order is important.
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When creating Instance you can set Properties using Initializers (must set all Properties that have no initial values)
● Default Initializer (it is used only if there are no Dedicated Initializers)
● Designated Initializers init(parameters) { ... } (Can call other Designated Initializers)
Only mutating Methods can change Property values (new instance is created with new values).
Struct can only adopt Protocols (can't extend Struct/Class).
Default Initializer & Mutating Methods
//DECLARE STRUCTURE.
struct Person {
//PROPERTIES.
var name : String //Value must be set through Default Initializer
var age : Int = 0 //Has initial value.
//METHODS.
mutating func greet () -> (String) { //Mutating Method changes age
self.age = 20 //Otherwise 'self' is immutable
return("\(name) is \(age) years old")
}
}
//CREATE INSTANCE.
var john = Person(name: "John") //Call Default Initializer (Create Instance)
print(john.greet()) //John is 20 years old
john.name = "Bill" //You can change Property Value
print(john.name) //Bill
print(john.age ) //20
Designated Initializers
//DECLARE STRUCT.
struct Person {
//DECLARE FIELDS.
var name : String //Value must be set through Designated Initializer
var age : Int //Value must be set through Designated Initializer
//DESIGNATED INITIALIZER (with 2 parameters)
init(name: String, age: Int) {
self.name = name
self.age = age
}
//DESIGNATED INITIALIZER (with 1 parameter)
init(name: String) {
self.init(name: name, age: 50) //Call Designated Initializer with default age
}
}
//CREATE INSTANCE.
var person1 = Person(name: "John", age: 20) //Call Designated Initializer.
var person2 = Person(name: "Bill") //Call Designated Initializer.
dump(person2)
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Class must have initializer if any of the Properties are missing default values
● Designated Initializers init (parameters) { body }
(Can't reference other Initializers in the same Class. Can reference Parent's Designated Initializer)
● Convenience Initializers convenience init (parameters) { body }
(Can reference other Convenience Initializers in the same Class. Chain must end referencing Designated Initializer)
Initializers
//DECLARE STRUCT.
class Person {
//DECLARE FIELDS.
var name : String //Value must be set through Initializers
var age : Int //Value must be set through Initializers
//DESIGNATED INITIALIZER (with 2 parameters)
init(name: String, age: Int) {
self.name = name
self.age = age
}
//DESIGNATED INITIALIZER (with 1 parameter)
convenience init(name: String) {
self.init(name: name, age: 50) //Call Designated Initializer with default age
}
}
//CREATE INSTANCE.
var person1 = Person(name: "John", age: 20) //Call Designated Initializer.
var person2 = Person(name: "John") //Call Designated Initializer.
dump(person2)
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Protocols declare Properties and Methods without implementation. (similar to Interface in other Languages)
Multiple Protocols can be adopted by Classes, Structures or Enumerators.
Implement Protocol
//DECLARE PROTOCOL.
protocol Person {
//DECLARE COMPUTED PROPERTIES.
var name : String { get set } //Can be implemented as Variable. Only var is valid.
var age : Int { get } //Can be implemented as Constant. Only var is valid.
//DECLARE METHODS.
func greet () -> (String)
}
//DECLARE STRUCT.
struct Employee : Person { //struct adopts Person Protocol
//DECLARE PROPERTIES.
var name : String //Implemented as Variable
let age : Int //Implemented as Constant
//DECLARE METHOD.
func greet () -> (String) { return("\(name) is \(age) years old ") }
}
//CREATE STRUCT INSTANCE.
var employee = Employee(name: "John", age: 20)
print(employee.greet())
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Extensions are used to add Computed Properties and Methods to: Classes, Structures, Enumerations or Protocols.
Extensions
//DECLARE STRUCT.
struct Employee {
//DECLARE PROPERTIES.
var name : String
var age : Int
}
//DECLARE EXTENSION.
extension Employee {
//ADD COMPUTED PROPERTIES.
var hello : String {
get { return("Hello \(name)") }
}
//DECLARE METHODS.
func greet () -> (String) { return("\(name) is \(age) years old") }
}
//REFERENCE EXTENSION'S COMPUTED PROPERTIES & METHODS.
var employee : Employee = Employee(name: "John", age: 20)
print(employee.hello)
print(employee.greet())
