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A pointer in Go is a special-purpose variable that stores the memory address of other variables and the point where the memory is located. It can also access the value stored in that memory location.

Pointer declaration in Go

var pointer_name *Data_Type

Operators used in function pointers

1. • • It is a dereference operator that declares a pointer variable. You can use it to access the value stored in the dereferenced address.
2. & − This is an address operator and is used to give the address of a variable.

Initializing a pointer in Go

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)
}

Output:

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

Note that the value stored in the myPointer variable is the address of the variable myVariable.

Using uninitialized pointers in Go

package main

import "fmt"

func main() {

    var myPointer *int

    fmt.Println("The value stored in 'myPointer' = ", myPointer)
}

Output:

The value stored in 'myPointer' =  <nil>

请注意, uninitialized pointers will have the default value of nil.

:=Using shorthand syntax for pointers in Go

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)
}

Output:

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, if you have used a pointer to declare a specified data type, you can only use the pointer to address the memory address of a variable of that specified data type.

:=The operator automatically recognizes the data type and ensures that the created pointer can handle the same data type.

Changing the value of a variable using pointers in Go

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)


}

Output:

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

Note that you can change the value of a pointer instead of assigning a new value to a variable. The value changed using the pointer is also reflected in the original value.

Creating pointers in Go using new() function

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)

}

Output:

The value stored in 'myPointer' =  0xc000016058
The value pointed by 'myPointer' after dereferencing =  2

请注意, using new()the function, you can directly create a pointer to an integer.

Passing pointers as arguments to functions in Go

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)

}

Output:

The value of myVariable before function call is: 2
The value of myVariable after function call is: 5

Notice that the function created above changes the value of the variable myVariable. The value changed inside the function is reflected outside the function because the pointer directly refers to the memory location where the variable is stored.

Passing the address of a variable as an argument to a function in Go

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)

}

Output:

The value of myVariable before function call is: 2
The value of myVariable after function call is: 5

请注意, the function created above changes the value of the variable myVariable. The value changed inside the function is reflected outside the function.

The changes are made to the memory location where the variable is stored. This is another way of passing a pointer to a function.

Returning a pointer from a function in Go

package main
import "fmt"

func main() {

  displayText := display()

  fmt.Println("Hello,", *displayText)

}

func display() *string {

  myMessage := "World!"

  return &myMessage

}

Output:

Hello, World!

请注意, the function created above will return a pointer to the string myMessage. This value is then dereferenced in the main function.