go 中的函数指针-ag捕鱼王app官网

go语言中的指针是一种具有特殊用途的变量，用于存储其他变量的内存地址和内存所在的点。 也可以访问存储在该内存位置的值。

go 中的指针声明

var pointer_name *data_type

函数指针中使用的运算符

1. • • 它是一个声明指针变量的取消引用运算符。 可以使用它访问存储在解除引用地址中的值。
2. & - 这是一个地址运算符，用于给出变量的地址。

在 go 中初始化一个指针

package main
import "fmt"
func main() {
    var myvariable int = 2
    var mypointer *int
    mypointer = &myvariable
    fmt.println("the value stored in 'myvariable' = ", myvariable)
    fmt.println("the address of 'myvariable' = ", &myvariable)
    fmt.println("the value stored in 'mypointer' = ", mypointer)
    fmt.println("the value pointed by 'mypointer' after dereferencing = ", *mypointer)
}

输出:

the value stored in 'myvariable' =  2
the address of 'myvariable' =  0xc000090020
the value stored in 'mypointer' =  0xc000090020.
the value pointed by 'mypointer' after dereferencing =  2

注意mypointer变量中存储的值是变量myvariable的地址。

在 go 中使用未初始化的指针

package main
import "fmt"
func main() {
    var mypointer *int
    fmt.println("the value stored in 'mypointer' = ", mypointer)
}

输出:

the value stored in 'mypointer' =  

请注意 ，未初始化的指针将具有默认的 nil 值。

在 go 中对指针使用简写 := 语法

package main
import "fmt"
func main() {
    myvariable := 2
    mypointer := &myvariable
    fmt.println("the value stored in 'myvariable' = ", myvariable)
    fmt.println("the address of 'myvariable' = ", &myvariable)
    fmt.println("the value stored in 'mypointer' = ", mypointer)
    fmt.println("the value pointed by 'mypointer' after dereferencing = ", *mypointer)
}

输出:

the value stored in 'myvariable' =  2
the address of 'myvariable' =  0xc000090020
the value stored in 'mypointer' =  0xc000090020
the value pointed by 'mypointer' after dereferencing =  2

请注意 ，如果您已使用指针声明指定数据类型，则您只能使用指针来处理该指定数据类型变量的内存地址。

:= 运算符自动识别数据类型并确保创建的指针可以处理相同的数据类型。

在 go 中使用指针更改变量的值

package main
import "fmt"
func main() {
    myvariable := 2
    mypointer := &myvariable
    fmt.println("the value stored in 'myvariable' = ", myvariable)
    fmt.println("the address of 'myvariable' = ", &myvariable)
    fmt.println("the value stored in 'mypointer' = ", mypointer)
    fmt.println("the value pointed by 'mypointer' after dereferencing = ", *mypointer)
    *mypointer = 5
    fmt.println("the updated value pointed by 'mypointer' after dereferencing = ", *mypointer)
    fmt.println("the updated value stored in 'myvariable' = ", myvariable)
}

输出:

the value stored in 'myvariable' =  2
the address of 'myvariable' =  0xc000016058
the value stored in 'mypointer' =  0xc000016058
the value pointed by 'mypointer' after dereferencing =  2
the updated value pointed by 'mypointer' after dereferencing =  5
the updated value stored in 'myvariable' =  5

请注意，您可以更改指针的值而不是为变量分配新值。 使用指针更改的值也反映在原始值中。

在 go 中使用 new() 函数创建指针

package main
import "fmt"
func main() {
    var mypointer = new(int)
    *mypointer = 2
    fmt.println("the value stored in 'mypointer' = ", mypointer)
    fmt.println("the value pointed by 'mypointer' after dereferencing = ", *mypointer)
}

输出:

the value stored in 'mypointer' =  0xc000016058
the value pointed by 'mypointer' after dereferencing =  2

请注意 ，使用 new() 函数，您可以直接创建一个指向整数的指针。

将指针作为参数传递给 go 中的函数

package main
import "fmt"
func myfunction(myvariable *int) {
    *myvariable = 5
}
func main() {
    var myvariable = 2
    fmt.printf("the value of myvariable before function call is: %d\n", myvariable)
    var mypointer *int = &myvariable
    myfunction(mypointer)
    fmt.printf("the value of myvariable after function call is: %d\n", myvariable)
}

输出:

the value of myvariable before function call is: 2
the value of myvariable after function call is: 5

请注意，上面创建的函数更改了变量 myvariable 的值。 函数中改变的值反映在函数外，因为指针直接引用变量存储的内存位置。

将变量的地址作为参数传递给 go 中的函数

package main
import "fmt"
func myfunction(myvariable *int) {
    *myvariable = 5
}
func main() {
    var myvariable = 2
    fmt.printf("the value of myvariable before function call is: %d\n", myvariable)
    myfunction(&myvariable)
    fmt.printf("the value of myvariable after function call is: %d\n", myvariable)
}

输出:

the value of myvariable before function call is: 2
the value of myvariable after function call is: 5

请注意 ，上面创建的函数更改了变量 myvariable 的值。 函数中更改的值反映在函数外部。

更改是对存储变量的内存位置进行的。 这是将指针传递给函数的另一种方法。

从 go 中的函数返回指针

package main
import "fmt"
func main() {
  displaytext := display()
  fmt.println("hello,", *displaytext)
}
func display() *string {
  mymessage := "world!"
  return &mymessage
}

输出:

hello, world!

请注意 ，上面创建的函数将返回一个指向字符串 mymessage 的指针。 然后在主函数中取消引用该值。