golang different packages

In Golang, different packages can call and reference each other, which provides the basis for Golang's modular design. So, how do we use different packages correctly in Golang? In this article, we will take a deep dive into the usage and considerations of different packages in Golang.

First, we need to know how to reference different packages. In Golang, you can use the import statement to introduce a package, as shown below:

import "packageName"

It should be noted that after using the import statement, the imported package Exportable identifiers (properties, methods, etc.) can be called and used, while non-exportable identifiers cannot be accessed.

Next, let’s take a look at how to make calls between different packages.

Suppose we have two packages, packageA and packageB, where packageA has a function funcA, we Want to call it in packageB. Then, in packageB, we need to import packageA through the import statement and call it in the following way:

package packageB

import "packageA"

func main() {
    packageA.funcA()
}

It should be noted that , in the above code, the packageA. before the funcA method indicates that the function is defined in packageA, not packageB The function. In addition, there is only a difference between uppercase and lowercase letters, and variable and function names in different packages can be the same. Therefore, to avoid confusion and errors, we should keep package names and variable/function names unique.

In Golang, all identifiers are private by default and can only be accessed in the package where they are located. However, exportable identifiers and non-exportable identifiers can be distinguished by the case of the first letter of the variable name and function name. . Specifically, capital letters in variable names and function names represent exportable identifiers, while lowercase letters represent non-exportable identifiers.

For example, the following function is defined in packageA:

package packageA

func FuncA() {
    fmt.Println("This is a public function.")
}

func funcA() {
    fmt.Println("This is a private function.")
}

Among them, FuncA is an exportable function that can be used in another package is called, and funcA is a private function and can only be used in the packageA package.

To prevent improper use, non-exportable identifiers should use private nomenclature: lowercase letters and underscore combinations (such as func_a).

If we need to share variables between different packages, we can use global variables in Golang. Global variables must be declared with the var keyword before the variable, otherwise the variable will be regarded as a function local variable. For example:

package packageA

var GlobalVar int = 100

In this way, we can reference this global variable in other packages. It should be noted that global variables may cause problems for multi-threaded scenarios, so you need to pay attention to multi-thread safety when using global variables.

In Golang, we can divide the same package by creating different files in the same folder. The code in each file belongs to the same package and can be directly called and referenced in other files. For example:

In the packageA directory, we create two files file1.go and file2.go:

// file1.go
package packageA

func FuncA() {
    fmt.Println("This is a public function.")
}

// file2.go
package packageA

func FuncB() {
    fmt.Println("This is another public function.")
}

The codes in these two files belong to the packageA package, and they can be called directly in other files.

Finally, it should be noted that between different packages, do not overuse global variables and function calls, which will reduce the readability and maintainability of the code. The correct practice is to reduce the visible scope of functions and variables to their own packages as much as possible to improve the readability and maintainability of the code structure.

In short, in Golang, different packages can call and reference each other, which provides the basis for Golang’s modular design. Use the import statement to introduce a package. When using methods and variables between different packages, you need to pay attention to the difference between exportable identifiers and non-exportable identifiers. At the same time, in order to improve the readability and maintainability of the code, reduce the visible scope of functions and variables to their own packages as much as possible, and avoid excessive use of global variables and function calls. These considerations will ensure that we can correctly reference and call functions and variables in other packages when using different packages.

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