Go Pointer Part II

By ski11up.com

September 28, 2020

In the previous blog-post Go Pointer Part I we have seen how we can use pointers to update the value for a given struct. There is little more left on that which we will cover here.

Go Slice is an exception and we can update the value of a slice with the index location but if we want to add more values to it then we need to use a pointer, let’s take a look at the same.

App

We will define a slice of contacts, initialize the same and perform an update and append operation on the same.

Code

Go code for updating contacts slice.

update_contact_slice.go

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  package main

  import "fmt"

  type contacts []string (1)

  func main() {
    firstName := contacts{"John", "Jagdeep"} (2)

    firstName.print()
    update(firstName)
    firstName.print()

    firstName.appendTo("Pradeep")
    firstName.print()
  }

  func update(c contacts) { (3)
    c[0] = "Jagdeep"
  }

  func (c *contacts) appendTo(name string) { (4)
    *c = append(*c, name)
  }

  func (c contacts) print() {
    for _, name := range c {
      fmt.Printf("\n%s ", name)
    }
  }

1	defining contacts slice
2	initializing the slice
3	simply pass the index location and update the value
4	receiver function, we are passing a contact pointer and using the inbuilt method to append the new contact

restrict using pointers only when you want to perform the update operation

Execute Go App

Navigate to the project folder and execute the below command.

  $ go run update_contact_slice.go

Notes

As you can see from the code that we have used index location to update the value of the contact slice but when we want to add more values to the slice then we have used pointers, this is an exception in Go, rest all requires a pointer to update anything.

Go Pointer