如何在go中定义一个指针，然后将该指针传递给func来更改其值？

问题描述：

import "fmt"

func zeroptr(ptr *int) {
    *ptr = 0
}

func main() {
    oneptr * int
    *ptr = 1
    fmt.Println("ptr is :", *ptr)
    zeroptr(ptr)
    fmt.Println("after calling zeroptr, the value of ptr is :", *ptr)
}

This does not work, I am looking for output as follows:

ptr is :1

after calling zeroptr, the value of ptr is : 0

  import“ fmt” 
 
func zeroptr（ptr * int）{
 * ptr = 0  
} 
 
func main（）{
 oneptr * int 
 * ptr = 1 
 fmt.Println（“ ptr is：”，* ptr）
 zeroptr（ptr）
 fmt.Println（“ 调用zeroptr之后，ptr的值为：“，* ptr）
} 
  code>  pre> 
 
 ，这不起作用，我正在寻找如下输出：  p> 
 
 
 ptr为：1  p> 
 
 
调用zeroptr后，ptr的值为：0  p> 
  div>

答

What does your pointer point to? In order to manipulate the memory a pointer points to, you first need to point the pointer somewhere. Right now, your ptr is pointing to nil which is invalid. You could for instance do this:

func main() {
    var foo int
    var oneptr *int = &foo
    *oneptr = 1
    fmt.Println("oneptr is :", *oneptr)
    zeroptr(oneptr)
    fmt.Println("after calling zeroptr, the value of oneptr is :", *ptr)
}

For the future, please indent your code before submitting it here. You can do this with the gofmt program.

答

You should use pass an &int to zeroptr, as in this example:

package main

import "fmt"

func zeroptr(ptr *int) {
    *ptr = 0
}

func main() {

    var ptr int
    ptr = 1
    fmt.Println("ptr is :", ptr)
    zeroptr(&ptr)
    fmt.Println("after calling zeroptr, the value of ptr is :", ptr)
}

Output:

ptr is : 1
after calling zeroptr, the value of ptr is : 0

You can see a similar example in "What's the point of having pointers in Go?", from the golang book.

如何在go中定义一个指针，然后将该指针传递给func来更改其值？

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