golang struct method

Golang is a modern high-performance programming language, and its unique data type struct (structure) is one of the most important components of the language. Not only that, in Golang, structures also support the definition of methods, so in this article, we will focus on the golang struct method.

I. What is golang structure?

In Golang, a structure is a user-defined data type that can encapsulate a set of related data fields. Structures are often used to describe complex data structures to better manage and use data.

A Golang structure definition usually contains several fields. The fields can be basic data types (such as int, float, etc.) or other structure types and pointer types. The following is a simple Golang structure definition example:

type Person struct {
    Name string
    Age int
    Address string
}

The above code defines a Person structure type, which contains three fields Name, Age and Address. It should be noted here that the case of the first letter of the structure field determines whether the field can be accessed by other packages (including the main package). How to access is shown in the following example:

package main

import (
    "fmt"
)

type Person struct {
    Name string
    age int //小写开头
    Address string
}

func main() {
    p1 := Person{"Bob", 30, "Beijing"}
    fmt.Println(p1.Name) // Bob
    fmt.Println(p1.Address) // Beijing
    fmt.Println(p1.age) // 编译错误，age未导出
}

II. Golang structure method Definition

In Golang, a structure method is a function that can access the fields of the structure and other related data, and can modify the field values ​​of the structure in the method. Methods can also return a value or an error if an error occurs during method execution. Any structure type can have methods, and methods can be defined in any package.

The definition of methods in Golang is similar to functions, but the receiver type needs to be specified in the definition. The receiver type can be a structure type or its pointer type (the pointer type here is similar to the reference type in C), representing the structure object that the method will operate on. The definition syntax of the method is as follows:

func (t Type) MethodName(parameterlist) (returntype) {
// function body
}

Among them, Type represents the type of the receiver, and MethodName is the method name, parameterlist defines the parameter list of the method, and returntype is the return type of the method. If there is no return value, then This part can be omitted.

The following is an example of a method for a structure:

type Rectangle struct {
     width float64
     height float64
}

func (r Rectangle) Area() float64 {
    return r.width * r.height
}

The above code defines a structure type named Rectangle, which contains two fields: width and height, and also defines An Area method is created, which returns the area of ​​the rectangle, where the receiver r is the rectangle itself.

III. Method calling of golang structure

The method calling method is similar to ordinary function calling, except that a receiver object needs to be added in front. Golang provides two calling methods for this.

The first is a value method call. When a method of a structure is called through a value method, a copy of the structure is first created, then the copy is operated and the result is returned. The following is an example of a value method call:

func main() {
     r := Rectangle{5, 10}
     a := r.Area() //调用值方法
     fmt.Println("area: ", a) //输出结果
}

The output result is:

area: 50

The second is a pointer method call. The method called through a pointer receives the pointer type and will directly access the original structure. They operate on entities and are therefore often more efficient than value methods. The following is an example of a pointer method call:

func (r *Rectangle) Scale(w, h float64) {
     r.width *= w
     r.height *= h
}

func main() {
     r := Rectangle{5, 10}
     r.Scale(2, 5) // 调用指针方法
     fmt.Println(r.width, r.height) // 输出结果
}

The output result is:

10 50

IV. Summary of golang structure methods

In this article, we learned about Golang The definition of the structure and the definition and invocation of methods. The struct structure type is an important component in the Golang language, which can encapsulate a related data collection. At the same time, methods extend the functionality of the structure, allowing programmers to better operate and manage the data in the structure. Finally, we need to note that the method can be a value method of the receiver type or a pointer method, so we need to choose the appropriate calling method in the actual application.

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