golang interface usage

Go language is a statically typed language with a rich type system. The interface is a unique type in the Go language and an important part of it. In this article, we will introduce the usage of golang interface in detail, including definition, implementation, usage, etc.

1. Define the interface

An interface is a set of methods that can be implemented between different types. Used to describe an abstract behavior. In Go language, you can use the type and interface keywords to define interfaces.

When using the type keyword to define an interface, the syntax format is as follows:

type interface_name interface {
    method_name1 [return_type]
    method_name2 [return_type]
    …
    method_namen [return_type]
}

In the above definition, interface_name is the name of the interface, method_namen is the method name of the interface, and return_type is the return of the method. Value type. If there is no return value, you do not need to fill in this part.

The following is an example that defines an interface named Shape, which includes a method named Area:

type Shape interface {
    Area() float64
}

We can also define multiple methods in the interface, for example:

type Shape interface {
    Area() float64
    Perimeter() float64
}

2. Implement the interface

In the Go language, the implementation of the interface is implicit. As long as a type has all the methods defined in the interface, then this type automatically implements the interface. . This approach is different from the explicit implementation in other languages ​​and is unique to the Go language.

The following is an example of implementing the Shape interface, defining two types: Rectangle and Circle. The code is as follows:

package main

import (
    "fmt"
    "math"
)

type Shape interface {
    Area() float64
}

type Rectangle struct {
    width, height float64
}

type Circle struct {
    radius float64
}

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

func (c Circle) Area() float64 {
    return math.Pi * c.radius * c.radius
}

func main() {
    var s Shape
    r := Rectangle{width: 5, height: 3}
    c := Circle{radius: 2.5}

    s = r
    fmt.Println("Rectangle area:", s.Area())

    s = c
    fmt.Println("Circle area:", s.Area())
}

In the above code, the Rectangle and Circle types implement the Area method in the Shape interface respectively. In the main function, we create a variable s of type Shape and assign it to an instance of type Rectangle and Circle respectively. We can calculate the area of ​​these two types by calling the s.Area() method. In the Go language, this way of using interfaces is very flexible and can easily implement programming patterns such as polymorphism and dependency injection.

3. Empty interface

In the Go language, all types implement an interface called empty interface, which is defined as follows:

type interface{}

The empty interface does not have any methods, so it can be used to represent any type, similar to the Object type in other languages. By using the empty interface, very flexible programming can be achieved, such as storing any type of value in a slice.

The following is an example of using an empty interface. A PrintAll function is defined, which can print out all elements in any type of slice:

package main

import (
    "fmt"
)

func PrintAll(slice []interface{}) {
    for _, value := range slice {
        fmt.Println(value)
    }
}

func main() {
    var slice []interface{}
    slice = append(slice, 42, "hello", true)

    PrintAll(slice)
}

In the above code, we define a The function named PrintAll accepts a parameter slice of type []interface{}. This function loops through the elements in the slice and prints them out. In the main function, we create a slice, add elements of type int, string, and bool to it and pass it to the PrintAll function. By using the empty interface, we can implement any type of element passing and calling.

4. Summary

In this article, we introduced the definition, implementation, and use of interfaces in the Go language. As one of the important features of the Go language, interfaces can achieve code flexibility and scalability. When using an interface, you need to pay attention to its implementation, type matching and other details. At the same time, we also introduced the use of empty interfaces and explained its importance and role in Go language programming.

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