How to store and get a pointer reference in a global scope in GO

huangapple
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英文:

How to store and get a pointer reference in a global scope in GO

问题

我已经得到了以下代码：

  1. package main
  3. func main() {
  4.     // 创建一个指向Mongo DB会话的指针引用
  5.     session := mongoDB.CreateSession()
  7.     // 问题1：如何在全局范围内存储指针引用，并在代码的任何地方使用它
  9.     defer session.Close()
  11.     // 注意：我假设代码调用处理程序方法，该方法调用控制器包中的Process方法（最后一个代码块）
  12. }

创建MongoDB会话的代码：

  1. package mongoDB
  3. func CreateSession() *mgo.Session {
  4.     session, err := mgo.Dial("192.168.0.108:27017/databasename")
  5.     if err != nil {
  6.         panic(err)
  7.     }
  8.     session.SetMode(mgo.Monotonic, true)
  9.     return session
  10. }

我想要在主函数中存储的指针引用的位置：

  1. package controller
  3. func Process() {
  4.     // 问题2：如果可能的话，如何获取存储在问题1中的指针引用
  5.     collection := mongoDB.CreateCollection(session, "namedatabase", "colectionData")
  6.     mongoDB.InsertData(collection, "Ale", "45646565")
  7. }

我的理解是，你想避免在项目的所有函数中传递指针引用session。

英文:

I have got the follow code:

  1. package main
  4. func main() {
  5.     // create  a pointer referece of session of Mongo DB
  6. session := mongoDB.CreateSession()
  7.     
  8.     // Question 1 : How to store a pointer reference in a global scope and using anywhere of the code  
  9.     
  10. defer session.Close()
  12.     // Note I suppose that the code call to handler methods that call to the Process in the package controller(the last one code)
  14. }

Code of creating a session of MongoDB

  1. package mongoDB
  4. func CreateSession() *mgo.Session {
  5. session, err := mgo.Dial("192.168.0.108:27017/databasename")
  6. if err != nil {
  7. 	panic(err)
  8. }
  9. session.SetMode(mgo.Monotonic, true)
  10. return session
  11. }

Place where I want to use the pointer reference that was store in the main

  1. package controller
  4. func Process()  {
  6.     // Question 2 : How can a get the pointer reference store in Question 1 if is posible
  7. collection := mongoDB.CreateCollection(session, "namedatabase", "colectionData")
  8. mongoDB.InsertData(collection, "Ale", "45646565")
  10. }

The idea is to avoid passing by reference session(my pointer reference in the main function) in every one of the functions created for all the project.

答案1

得分: 0

你的controller包不能导入main包。这不是一个好主意（我相当确定这是不可能的）。但这并不意味着你不能在controller中有一个全局的session变量。

你可以尝试以下代码：

  1. package main
  3. import (
  4. 	"controller"
  5. 	"mongoDB"
  6. )
  8. func main() {
  9. 	// 创建Mongo DB会话的指针引用
  10. 	session := mongoDB.CreateSession()
  11. 	defer session.Close()
  12. 	
  13. 	controller.SetDBSession(session) // 或者使用controller.Init或其他你喜欢的方式
  15. 	controller.Process()
  16. }

然后在controller包中：

  1. package controller
  3. import "mongoDB"
  5. // 该包的全局session变量
  6. var session mongoDB.Session
  8. // SetDBSession将mongoDB会话设置为controller包要使用的会话。
  9. // 在调用Process()之前必须调用此函数。
  10. func SetDBSession(s mongoDB.Session) {
  11. 	session = s
  12. }
  14. func Process() {
  15. 	collection := mongoDB.CreateCollection(session, "namedatabase", "colectionData")
  16. 	mongoDB.InsertData(collection, "Ale", "45646565")
  17. }

使用这个解决方案，你只需要将会话传递给controller包一次，让main负责创建和关闭会话。

英文:

You can't have your controller package import main. That is not a good idea (and I am quite sure it is not even possible). But that doesn't mean you can't have a global session variable in the controller.

You can try this:

  1. package main
  3. import (
  4. 	"controller"
  5. 	"mongoDB"
  6. )
  8. func main() {
  9. 	// create  a pointer referece of session of Mongo DB
  10. 	session := mongoDB.CreateSession()
  11. 	defer session.Close()
  12. 	
  13. 	controller.SetDBSession(session) // Or controller.Init or whatever you like
  15. 	controller.Process()
  16. }

And then in the controller package you have:

  1. package controller
  3. import "mongoDB"
  5. // Global session var for the package
  6. var session mongoDB.Session
  8. // SetDBSession sets the mongoDB session to be used by the controller package.
  9. // This function must be called before calling Process()
  10. func SetDBSession(s mongoDB.Session) {
  11. 	session = s
  12. }
  14. func Process() {
  15. 	collection := mongoDB.CreateCollection(session, "namedatabase", "colectionData")
  16. 	mongoDB.InsertData(collection, "Ale", "45646565")
  17. }

Using this solution, you will only have to pass the session to the controller package once, letting main take care of the creating and closing of the session.

huangapple
  • 本文由 发表于 2014年4月23日 05:51:39
  • 转载请务必保留本文链接：https://go.coder-hub.com/23230888.html
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