golang init method

Go language is a strongly typed, compiled language that introduces a special function-init() function. The init() function, like the main() function, is a reserved function in the Go language, except that the init() function has no entry parameters and no return value.

The init() function is the first function to be executed before the program is executed. As long as the package is imported, the init() function will be automatically executed. In other words, the init() function can be regarded as the constructor of a package, used to initialize some data required by the package or perform some necessary operations.

Multiple init() functions can be defined in a package, and they will be executed in the order defined. However, this is not recommended because the order in which multiple init() functions are executed may be very unpredictable. Therefore, the only suggestion is to try to avoid defining multiple init() functions in a package unless it is really necessary to perform some initialization operations in sequence.

Let’s use some examples to better understand the role of the init() method:

First example:

package main

import "fmt"

func init() {
    fmt.Println("init方法被调用")
}

func main() {
    fmt.Println("main方法被调用")
}

After running the program, you will see The following output:

init方法被调用
main方法被调用

From this example, we can see that the init() method will be executed before the main() method no matter what. Therefore, we can use the init() method to initialize global variables or call functions in other packages, etc.

Second example:

package packageA

import "fmt"

func init() {
    fmt.Println("packageA中的init方法被调用")
}

package packageB

import (
    "fmt"
    "packageA"
)

func init() {
    fmt.Println("packageB中的init方法被调用")
}

func Test() {
    packageA.init()
}

package main

import (
    "fmt"
    "packageB"
)

func main() {
    fmt.Println("main方法被调用")
    packageB.Test()
}

Running the above program will get the following output:

packageA中的init方法被调用
packageB中的init方法被调用
main方法被调用
packageA中的init方法被调用

From the output, we can clearly see: when we import packageB , first the init() method in packageA is executed, then the init() method in packageB is executed, and finally the main() method is executed. When we call the Test() method of packageB in the main() method, because the init() method in packageA has already been executed, the init() method of packageA will not be called again.

In short, the init() function plays a very important role and is one of the necessary components for program running. Whether you define the init() function in a package or call the init() function in another package, you need to understand the relevant characteristics of the init() function in order to better use the Go language for program development.

The above is the detailed content of golang init method. For more information, please follow other related articles on the PHP Chinese website!