Why Do I Need a Pointer Receiver to Remove an Element from a Slice in a Struct?

Removing an Element from a Slice in a Struct

To remove an element from a slice in a struct, you must use a pointer receiver, rather than a value receiver. A value receiver modifies a copy of the original struct, while a pointer receiver modifies the original struct itself.

Code Example

Consider this code to remove a friend from a Guest struct:

type Guest struct {
    id      int
    name    string
    surname string
    friends []int
}

func (self Guest) removeFriend(id int) {
    for i, other := range self.friends {
        if other == id {
            self.friends = append(self.friends[:i], self.friends[i+1:]...)
            break
        }
    }
}

This code will not work because it uses a value receiver, (self Guest). To modify the original struct, you must use a pointer receiver, (self Guest)*.

Correct Code

func (self *Guest) removeFriend(id int) {
    for i, other := range self.friends {
        if other == id {
            self.friends = append(self.friends[:i], self.friends[i+1:]...)
            break
        }
    }
}

Now, calling guest1.removeFriend(3) will remove the friend with ID 3 from the guest1 struct.

Note:

Also note that using receiver names like (self) and (this) is not idiomatic in Go. Instead, use the name of the struct, such as (guest).

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