Swift class

Swift class is the code used to build a general and flexible structure.

We can define the properties (constants, variables) and methods for the class.

And other programming languages ​​are different, Swift does not require you to create custom classes to separate interface and implementation files. You have to do it is to define a class in a single file, the system will automatically generate the code for other external interfaces.

Body type and structure comparison

Swift classes and structures have much in common. Common is that:

• Defined attributes used to store values
• Defines a method for providing functionality
• Defined script is used to access the value of the subsidiary
• Define the constructor is used to generate initialization value
• By extending the functions implemented in order to increase the default
• In line with the agreement to provide certain standard functions

Compared with the structure, class has the following additional features:

• Inheritance allows a class inherits from another class feature
• Type conversion allows runtime type checking and interpretation of a class instance
• Deconstruction allows a class instance to release any resources it allocated
• Reference counting allows multiple references to a class

grammar:

Class classname {
   Definition 1
   Definition 2
   ……
   Definition N
}

Class definition

class student{
   var studname: String
   var mark: Int 
   var mark2: Int 
}

Instantiate the class:

let studrecord = student()

Examples

import Cocoa

class MarksStruct {
    var mark: Int
    init(mark: Int) {
        self.mark = mark
    }
}

class studentMarks {
    var mark = 300
}
let marks = studentMarks()
print("成绩为 \(marks.mark)")

The above program execution output is:

成绩为 300

As reference types Class attribute

Attributes of the class can be accessedthrough.The format is:instantiate class name property name:

import Cocoa

class MarksStruct {
   var mark: Int
   init(mark: Int) {
      self.mark = mark
   }
}

class studentMarks {
   var mark1 = 300
   var mark2 = 400
   var mark3 = 900
}
let marks = studentMarks()
print("Mark1 is \(marks.mark1)")
print("Mark2 is \(marks.mark2)")
print("Mark3 is \(marks.mark3)")

The above program execution output is:

Mark1 is 300
Mark2 is 400
Mark3 is 900

Identity operator

Because classes are reference types, there may be a plurality of constants and variables at the same time a reference to a class instance in the background.

In order to determined whether the two constants or variables refer to the same class instance, Swift built two identical operators:

Examples

import Cocoa

class SampleClass: Equatable {
    let myProperty: String
    init(s: String) {
        myProperty = s
    }
}
func ==(lhs: SampleClass, rhs: SampleClass) -> Bool {
    return lhs.myProperty == rhs.myProperty
}

let spClass1 = SampleClass(s: "Hello")
let spClass2 = SampleClass(s: "Hello")

if spClass1 === spClass2 {// false
    print("引用相同的类实例 \(spClass1)")
}

if spClass1 !== spClass2 {// true
    print("引用不相同的类实例 \(spClass2)")
}

The above program execution output is:

引用不相同的类实例 SampleClass