Golang Pointer to an Array as Function Argument

Prerequisite: Pointers in Golang

Pointers in Go programming language or Golang is a variable which is used to store the memory address of another variable. Whereas an array is a fixed-length sequence which is used to store homogeneous elements in the memory.

You can use the pointers to an array and pass that one as an argument to the function. To understand this concept let’s take an example. In the below program we are taking a pointer array arr which has 5 elements. We want to update this array using a function. Means modifying the array(here the array is {78, 89, 45, 56, 14}) inside the function and that will reflect at the caller. So here we have taken function updatearray which has pointer to array as argument type. Using updatearray(&arr) line of code we are passing the address of the array. Inside function (*funarr)[4] = 750 or funarr[4] = 750 line of code is using dereferencing concept to assign new value to the array which will reflect in the original array. Finally, the program will give output [78 89 45 56 750].



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// Golang program to pass a pointer to an
// array as an argument to the function
package main
  
import "fmt"
  
// taking a function
func updatearray(funarr *[5]int) {
  
    // updating the array value
    // at specified index
    (*funarr)[4] = 750
      
    // you can also write 
    // the above line of code
    // funarr[4] = 750
}
  
// Main Function
func main() {
  
    // Taking an pointer to an array
    arr := [5]int{78, 89, 45, 56, 14}
  
    // passing pointer to an array
    // to function updatearray
    updatearray(&arr)
  
    // array after updating
    fmt.Println(arr)
}

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Output:

[78 89 45 56 750]

Note: In Golang it is not recommended to use Pointer to an Array as an Argument to Function as the code become difficult to read. Also, it is not considered a good way to achieve this concept. To achieve this you can use slice instead of passing pointers.

Example:

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// Golang program to illustrate the
// concept of passing a pointer to an
// array as an argument to the function
// using a slice
package main
  
import "fmt"
  
// taking a function
func updateslice(funarr []int) {
  
    // updating the value
    // at specified index
    funarr[4] = 750
}
  
// Main Function
func main() {
  
    // Taking an slice
    s := [5]int{78, 89, 45, 56, 14}
  
    // passing slice to the
    // function updateslice
    updateslice(s[:])
  
    // displaying the result
    fmt.Println(s)
}

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Output:

[78 89 45 56 750]


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