golang has no class

Objects and classes in Go language

Among many programming languages, Object-Oriented Programming (OOP) is a popular programming paradigm that packages data and methods in together to create modular, reusable code. In traditional OOP languages ​​(such as Java, C, etc.), classes are one of the core concepts of OOP. Features such as encapsulation, inheritance, and polymorphism can be achieved through classes. But in Go language, there is no class keyword, and OOP in Go language is different from traditional OOP language in many ways.

Object-oriented in Go language

In Go language, object-oriented implementation is mainly implemented through structures (Struct) and methods (Method). These methods can be combined with structures Association to form an object. In the Go language, structures are defined in a similar way, and they can also contain member variables and member methods.

The definition of a simple Go structure is as follows:

type Person struct {
    Name    string
    Age     int
    Address string
}

In this example, we define a structure named Person, which contains three fields: Name, Age and Address . The member variables of this structure can be accessed through "." syntax, for example:

var person Person
person.Name = "Tom"
person.Age = 20
person.Address = "New York"

In this way, we create an instance named person, and the fields can be accessed through ".".

Through the structure, we can define the attributes (member variables) of the instance, but how to operate the instance? In the Go language, you can define methods for a structure and operate the member variables of the structure within the method.

The definition of a simple Go method is as follows:

func (p *Person) GetAge() int {
    return p.Age
}

In this example, we define a method named GetAge, which returns the age (Age) of the current structure instance. It should be noted that this method uses a pointer type receiver, which means that it can modify the properties of the structure instance.

Creation and use of objects

The way to create objects in Go language is also different from other OOP languages. In traditional OOP languages, we can create objects through keywords such as "new" or "constructor". But in Go language, we only need to create an instance through the structure definition, and then pass the pointer of the instance to the method for operation.

A simple example of creating and using Go objects is as follows:

var person *Person = new(Person)
person.Name = "Tom"
person.Age = 20
person.Address = "New York"
fmt.Println("The age of person is", person.GetAge()) // 输出 The age of person is 20

In this example, we first create an instance named person through the new() function, and then set it properties. Finally, we call the person's GetAge() method to get the person's age.

It should be noted that in Go language, you can use the "&" operator to get a pointer to a variable, for example:

var person Person
var p *Person = &person

Here, we first define a variable named person Structure instance, then use the "&" operator to obtain its pointer, and assign the pointer to the p variable. You can also directly use the "&" operator to get the pointer of a newly created structure instance, for example:

var p *Person = &Person{}

In this way, we create a Person object named p and assign its pointer to the p variable.

Inheritance and polymorphism

In traditional OOP languages, inheritance and polymorphism are two very important features. They can greatly improve code reusability and flexibility. However, in the Go language, since there is no class keyword, the implementation of inheritance and polymorphism are somewhat different.

In Go language, inheritance is implemented through "Embedded Struct". This is very similar to inheritance in the Java language, but unlike Java, the nested structure in the Go language does not inherit all members of the parent structure by default.

An example of a simple Go nested structure is as follows:

type Driver struct {
    Name string
}

type Car struct {
    *Driver
    Brand string
}

func (d *Driver) Drive() {
    fmt.Println(d.Name, "is driving")
}

func main() {
    var john *Driver = &Driver{Name: "John"}
    var benz *Car = &Car{Driver: john, Brand: "Benz"}
    benz.Drive() // 输出 John is driving
}

In this example, we define a structure named Driver and a structure named Car. Driver is nested in Car. The Driver structure has a method called Drive, which is used to output the driver's name. We can see that the Driver is nested in the Car, and the Driver's Drive method can be called through the Car instance. This implements simple inheritance.

In the Go language, polymorphism can be achieved using the "Interface" method. Different from traditional OOP languages ​​such as Java, the implementation of the interface is defined by the keyword "implements" (such as the "implements" keyword in Java), which is implemented implicitly in the Go language. You only need to define a method set. As long as the type that implements this method set can implement the interface, there is no need to explicitly declare that it implements the interface.

An example of a simple Go interface is as follows:

type Animal interface {
    Speak() string
}

type Dog struct{}

func (d Dog) Speak() string {
    return "Woof!"
}

type Cat struct{}

func (c Cat) Speak() string {
    return "Meow!"
}

func main() {
    var animal Animal = Dog{}
    fmt.Println(animal.Speak()) // 输出 Woof!
    animal = Cat{}
    fmt.Println(animal.Speak()) // 输出 Meow!
}

In this example, we define an interface named Animal and a method named Speak in it. We also created two types, Dog and Cat, both of which implement the Animal interface. Finally, we use the dynamic nature of the animal interface, assign it to instances of Dog and Cat types, and call their corresponding Speak methods. As you can see, through the interface, we have achieved simple polymorphism.

Summarize

Although there is no class keyword in the Go language, through the combination of structures and methods, we can also achieve object-oriented programming, including features such as encapsulation, inheritance, and polymorphism. And because there is no complexity of classes, object-oriented programming in Go language is more concise and flexible. At the same time, the Go language also provides features such as interface and embedded struct to implement polymorphism and inheritance. These features allow the Go language to maintain the simplicity and efficiency of the language while implementing OOP.

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