CODEWITHSUNDEEP
go
Hakan Baba
Hakan Baba

Reputation: 2045

How to modify a slice element which is a struct in golang?

You have a golang slice of structs and you would like to change one entry in there. 

type Type struct {
    value int
}

func main() {

    s := []Type{{0}, {0}}

    // Prints  [{0} {0}]
    fmt.Println(s)

    firstEntry := s[0]
    firstEntry.value = 5

    // Also prints [{0} {0}]
    fmt.Println(s)
}

https://play.golang.org/p/32tpcc3-OD

Using the brackets operator and modifying its return does not change the slice itself.

What is the recommended way of doing this slice entry modification ?

Upvotes: 29

Views: 36591

Answers (2)

Tristian
Tristian

Reputation: 3512

You can also take the address of the slice element directly and de-reference it:

func main() {

    s := []Type{{0}, {0}}

    // Prints  [{0} {0}]
    fmt.Println(s)

    // De-reference the address of the slice element
    (&s[0]).value = 5

    // Prints [{5} {0}]
    fmt.Println(s)
}

Upvotes: 6

WeakPointer
WeakPointer

Reputation: 3322

Try

s[0].value = 5

This gets to the backing store of the slice. Also

p := &s[1]
p.value = 6

Upvotes: 47

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