我应该传递指针作为参数吗？ [英] Should I pass pointers as parameters

问题描述

我有两个函数 main 和其他。如果我想在 other 函数中提供的 main 函数中有一个变量，我应该通过它作为参数还是击败指针的对象？

选项1

 func main（）{
 myVar：=hello world
 other（&myVar）
} 
 
 func其他（s *字符串）{
 println（s）
} 
  

选项2

  func main（）{
 myVar：=hello world
 other（）
} 
 
 func other（）{
 println（* myVar）//是否可以在此处访问myVar？ 
 
  

解决方案

downvoted ...第二个选项不会编译，因为在其他函数myVar不存在。每个变量都有一个范围。

（如果您想了解更多有关不同范围的内容，我建议您使用以下链接 https://www.golang-book.com/books/web/01-02 - 为了让事情更清楚一些，我添加了一些例子：

b
$ b

选项1 - 传递指针值

这就是你所拥有的。但请确保取消引用您的指针以获取实际的字符串。你的版本正在打印指针本身（mem-address）。

  func main（）{
 myVar：=hello世界
其他（& myVar）
} 
 
 func其他（s *字符串）{
 println（* s）
} 
  

选项2 - 传递变量值

这可能是您的选择2的意思。

 包主
 
 func main（）{
 myVar：=hello world
 other（myVar）
} 
 
 func other（myVar string）{
 println（ myVar）
} 
  

选项3 - 使myVar成为全球

也许这就是您想要在第二个选项中执行的操作。 myVar在这里是全球性的（或者像golang lingo一样，myVar有一个包级别的作用域），因此可以在其他函数中访问。

<$ p $






$ b func main（）{
> var myVar =hello world （）{
println（myVar）
}

你的问题是你应该传递一个值还是一个指向变量的指针：

一般来说，如果你的函数需要编辑值。另外，当变量本身非常大，并且花费时间/资源来传递值时，您可以传递更有效的指针。

I'm working with pointers for the first time and I have what is probably a simple question.

I have two functions main and other. If I have a variable in the main function that I would like to make available in the other function should I pass it as a parameter or is that defeating the object of pointers?

OPTION 1

func main() {
    myVar := "hello world"   
    other(&myVar)
}

func other(s *string) {
    println(s)
}

OPTION 2

func main() {
    myVar := "hello world"
    other()   
}

func other() {
    println(*myVar) //Is myVar even accessible here?
}

解决方案

Not sure why you've got downvoted... The second option will not compile because inside the other function myVar is not present. Every variable has a scope. The variable is only accessible inside it's scope.

(If you like to learn more about the diffrent scopes in go I recommend the following link https://www.golang-book.com/books/web/01-02 - scroll down to scope. It's well explained with a nice visualization.)

To make things a bit clearer, I add some examples:

OPTION 1 - pass the pointer value

This is what you had. But make sure to dereference your pointer to get back the actual string. Your version was printing the pointer itself (mem-address). See my change (*s instead of just s)!

func main() {
    myVar := "hello world"
    other(&myVar)
}

func other(s *string) {
    println(*s)
}

OPTION 2 - pass the variable value

This is probably what you meant with your option 2.

package main

func main() {
    myVar := "hello world"
    other(myVar)
}

func other(myVar string) {
    println(myVar) 
}

OPTION 3 - make myVar global

Maybe this is what you wanted to do in your second option. myVar is global here (or as in golang lingo, myVar has a package-level scope), therefore accessible inside the other function.

var myVar = "hello world"

func main() {
    other()
}

func other() {
    println(myVar)
}

As to your question wether you should pass the value or a pointer to the variable:

In general you pass pointers, if your function needs to be able to edit the value. Also when the variable itself is really big and it would cost time / ressources to pass the value you can pass the pointer which is more efficent.

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