reflect Call method on nested struct

[Sotirios Mantziaris]

Hi,

i have a nested struct and i want to call a method on a field.

type String struct {

value string

}

func (s *String) Set(value string) {

s.value = value

}

type Config struct {

Name String

}

I am getting the nested "Name" struct but there are no methods to call.

What am i doing wrong (besides using reflection :))?

Check out the playground link?

https://play.golang.org/p/XSRG5rFWdhq

[Jan Mercl]

On Wed, May 29, 2019 at 9:42 AM Sotirios Mantziaris
<smant...@gmail.com> wrote:

> I am getting the nested "Name" struct but there are no methods to call.
> What am i doing wrong (besides using reflection :))?

The method has a pointer receiver: https://play.golang.org/p/qjhqSvhE9PL

[Sotirios Mantziaris]

you are a live saver. thanks very much.
reflection is of of these things in any language i suppose.

--

Regards,

S. Mantziaris

[Sotirios Mantziaris]

I did found out that the setter method has to accept a pointer to string.
I have a complete example now which unfortunately don't work correclty. The value should change but it is emptied out.

https://play.golang.org/p/OPZKltApEhF

What am i missing?

[Sotirios Mantziaris]

Ok, found it. I should have used the reflect.ValueOf...

[Max]

There is another improvement you can do: you are currently using

cfg := Config{Name: &nameField}

r := reflect.ValueOf(cfg)

which means that 'r' will contain a copy of 'cfg' and will not be settable.

If instead you use:

r := reflect.ValueOf(&cfg).Elem()

then r will contain a *pointer* to the original 'cfg' and can modify it (the reflect.Value 'r' is settable).

In turn, this also allows to declare 'Config' as follows:

```

type Config struct {
    Name String
}

```

i.e. removes the need to use a *pointer* to String.

You also need some minor adjustments to the rest of the code...

A complete example is:

https://play.golang.org/p/AxPE0K_ivxP

[Sotirios Mantziaris]

Hi Max, 

this makes the config even simpler since i do not need to be sure that the field is nil.
I will try this out for sure.