Passing by value or passing by reference is more efficient in GoLang?

Question

Let's say I have a struct implementing an interface like below:

type IFace interface {
   Method1()
   Method2()
   Method3()
} 


type Face struct {
  Prop1 string
  Prop2 int
}


// IFace implementation here...

Now if I have method that accepts IFace is it better to design it to accept a pointer to that interface of value?

Accept pointer:

func DummyMethod(f *IFace) {
   (*f).Method1()
}

By value:

    func DummyMethod(f IFace){
      f.Method1()
    }

My first guess is since these are structs, probably it's better to pass by value? Or is there a rule of thumb considering the size and nature of the struct when to start passing a pointer?

Also, when we are adding methods to a struct is it better to pass a pointer to the struct or it's value?

See Pass Values and Receiver Types for recommendations.

user5728991
– user5728991

2019-02-24 04:32:57 +00:00
Commented Feb 24, 2019 at 4:32 — user5728991
– user5728991, Commented Feb 24, 2019 at 4:32

Adrian · Accepted Answer · 2019-02-24 05:25:55Z

1

When passing interface type as a parameter, pass it by value, note that interface type itself would be a pointer to concrete type.

When it comes to the performance side, using interface comes with the price too, it simply cannot be inlined.

I guess it is fine to use interface with dozen calls per request/entry point, but if an app has to make thousands+ invocations, benchmark your code first before making a call.

edited Feb 24, 2019 at 5:25

answered Feb 24, 2019 at 4:53

Adrian

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2 Comments

kovac Over a year ago

So even in the 2 case, what is actually passed is the value of the pointer to the concreate type and no copying of the concrete type happens?

Adrian Over a year ago

when passing a value there is always a copy involved, either copying a pointer or concrete value. Since the interface is already a pointer to a concrete type, no concrete type copying happens

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