Struct variable not being updated

Question

I have an array in test code

arr := []Server{}

which asks for arr[0].GetId()

Server is an interface. ServerInstance is a struct implementing a method of interface, i.e

func (serv ServerInstance) GetId() int {
    return serv.Id
}

I have a goroutine like

func (serv *ServerInstance) someFunc

which is updating a variable 'Id' of struct. I am sure of value being updated as -

serv.Id=23445

But this is not being reflected in call at line 3

*Update***

for somecondition {
     arr=append(arr,FuncReturningServerIntercae() // calling this invokes goroutine which keeps updating `Id` very frequently
}


for {
   for _,s := range arr {
        print s.GetId()   // ** No Update **
     }
    sleep(some duration)
}

** Example ** http://play.golang.org/p/zUqJ0hEjxv

well you are sure, but you wiill have to show some code for somone to help — Arjan
– Arjan, Commented Feb 14, 2014 at 18:16
If the call at line 3 is in a separate goroutine, it's possible that your id hasn't been updated yet? — weberc2
– weberc2, Commented Feb 14, 2014 at 18:24
just after the assignmet serv.Id=23445 , I printf to verify — Palash Kumar
– Palash Kumar, Commented Feb 14, 2014 at 18:27
There are a lot of things that could go wrong... It's hard to say without seeing a small, simple example. Can you boil it down to the relevant snippet and post the code or a link to play.golang.org or some such? — weberc2
– weberc2, Commented Feb 14, 2014 at 18:29

Stasis · Accepted Answer · 2014-02-14 19:46:22Z

3

You're copying the structs when appending them, rather than placing pointers to the structs themselves in the example. http://play.golang.org/p/rQz9RLTzMU -- works as intended yes? Further info: Golang is a pass-by-value language, so if you're using goroutines and you want to keep the sanctity of your data, you'd be better off using pointers.

edited Feb 14, 2014 at 19:46

answered Feb 14, 2014 at 19:07

Stasis

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1 Comment

Stasis Over a year ago

I get "Snippet not found" from that link.

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