How to define and use custom types using Go language?

In Go, custom types can be defined using the type keyword (struct) and contain named fields. They can be accessed through field access operators and can have methods attached to manipulate instance state. In practical applications, custom types are used to organize complex data and simplify operations. For example, a student management system uses a custom type Student to store student information and provide methods for calculating grade point average and attendance.

How to use the Go language to define and use custom types

In the Go language, custom types are a powerful feature that allows you to define own complex type to meet specific needs. This way you can organize your code, improve readability, and reduce errors.

Define a custom type

Use the type keyword to define a new custom type:

type Person struct {
    name string
    age  int
}

In this example, we define A type named Person that has two fields: name (a string) and age (an integer).

Accessing and manipulating custom types

Once a custom type is defined, you can create variables of that type and access its fields:

// 创建一个 Person 类型的新实例
person := Person{name: "John", age: 30}

// 访问 person 实例的字段
fmt.Println(person.name) // "John"
fmt.Println(person.age)  // 30

Methods

Custom types can define methods, which are functions attached to the type. Methods can access and modify the status of type instances:

type Person struct {
    name string
    age  int
}

func (p Person) Greet() {
    fmt.Println("Hello, my name is", p.name)
}

func main() {
    person := Person{name: "John", age: 30}
    person.Greet() // "Hello, my name is John"
}

Practical Case: Student Management System

Let us use a practical case to show how custom types can be used to solve practical problems. Consider a student management system where you need to track student information such as names, grades, and attendance.

type Student struct {
    name     string
    grades   []float64
    attendance float64
}

func (s Student) GetAverageGrade() float64 {
    total := 0.0
    for _, grade := range s.grades {
        total += grade
    }
    return total / float64(len(s.grades))
}

func main() {
    students := []Student{
        {name: "John", grades: []float64{90, 85, 95}, attendance: 0.9},
        {name: "Jane", grades: []float64{80, 90, 85}, attendance: 0.8},
    }

    for _, s := range students {
        fmt.Println("Student:", s.name)
        fmt.Println("Average Grade:", s.GetAverageGrade())
        fmt.Println("Attendance:", s.attendance)
        fmt.Println()
    }
}

In this example, the Student type has name, grade, and attendance fields. The GetAverageGrade method calculates a student's average grade, while the main function demonstrates how to use a custom type to create a student instance and access its information.

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