Or you can use a setter method:
https://go.dev/play/p/W9Cz2PO8NeK
On Saturday, 24 May 2025 at 03:39:34 UTC+1 Def Ceb wrote:
> You're creating new copies of the values and modifying the copies, rather
> than storing a reference and then modifying the original data through it.
> You'd use *string and *bool there to have both change.
> This would be somewhat tedious and involve a good amount of type casting
> though, if you were to keep doing it with interfaces like this. It could
> well be that you'd be better served by avoiding them in this instance. But
> if you must, then learn to enjoy type switches.
>
> On Sat, May 24, 2025, 05:17 'jlfo...@berkeley.edu' via golang-nuts <
> golan...@googlegroups.com> wrote:
>
>> I'm trying to write a program (see below) that passes a slice of structs
>> to a function. One of the struct fields is an interface{} that sometimes
>> will hold a boolean value and other times will hold a string value. To do
>> this, I put either a bool or a string variable in the field.
>>
>> What I want to happen is for the local variable to be assigned a value.
>> But, what's happening instead is only the struct field is assigned the
>> value.
>>
>> Here's the program: (also at https://go.dev/play/p/7y5COCLU5EP)
>>
>> package main
>>
>> import (
>> "fmt"
>> )
>>
>> type i_t struct {
>> arg interface{}
>> }
>>
>> func main() {
>>
>> var help bool = false
>> var fish string = "init"
>>
>> var i = []i_t{{help}}
>> var t = []i_t{{fish}}
>>
>> fmt.Printf("before: help = %t\tstruct = %t\n", help, i)
>> change_bool1(i)
>> fmt.Printf("after: help = %t\tstruct = %t\n", help, i)
>>
>> fmt.Println()
>>
>> fmt.Printf("before: fish = %s\tstruct = %s\n", fish, t)
>> change_string1(t)
>> fmt.Printf("after: fish = %s\tstruct = %s\n", fish, t)
>>
>> }
>>
>> func change_bool1(a []i_t) {
>>
>> a[0].arg = true
>> }
>>
>> func change_string1(a []i_t) {
>>
>> a[0].arg = "fish"
>> }
>>
>> It generates the following output:
>>
>> before: help = false struct = [{false}]
>> after: help = false struct = [{true}]
>>
>> before: fish = init struct = [{init}]
>> after: fish = init struct = [{fish}]
>>
>> You can see that the values of the variables aren't changing but the
>> values of the
>> struct fields are. Is there some way for both to change?
>>
>> Cordially,
>> Jon Forrest
>>
>>
>>
>>
>>
>> --
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>>
>> <https://groups.google.com/d/msgid/golang-nuts/bd06269a-7b6d-442a-a3f2-9d4f0020ac90n%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
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