reflect: how to initialize a struct field that is a map?

[Hai Thanh Nguyen]

For example we have a struct:
type Test struct {

   f map[string]string

}

if we initialize an instance of that struct with

o := reflect.New(reflect.TypeOf(Test{}))

now the field f is nil

I attempt to set the field f to a new map:

o.FieldByName("f").Set(reflect.MakeMap(...))

however this fails because the field is nil, it cannot be set

so how do I initialize the field?
basically it's something like `o.f = make(map[string]string)`

[egon]

You cannot set private fields with reflection.

[Hai Thanh Nguyen]

Oh sorry I was in a hurry and typed it wrong, it should have been F, this question is not about that (ofc. I know reflection doesn't work with unexported field).
It's about Initializing a field which is a map that is nil when the struct get created.

Question rewritten:

For example we have a struct:
type Test struct {

   F map[string]string

}

if we initialize an instance of that struct with

o := reflect.New(reflect.TypeOf(Test{}))

now the field F is nil

I attempt to set the field F to a new map:

o.FieldByName("F").Set(reflect.MakeMap(...))

however this fails with something like "cannot set to zero value" because the field is nil, it cannot be set

so how do I initialize the field?

basically it's something like `o.F = make(map[string]string)`

[Carlos Castillo]

You cant set the field of a pointer (it doesn't have fields), you must use Elem, to get the actual struct.

Also, you should use the playground: http://play.golang.org/p/ovPA6i7g_r

[egon]

On Sunday, 15 June 2014 21:07:30 UTC+3, Hai Thanh Nguyen wrote:

Oh sorry I was in a hurry and typed it wrong, it should have been F, this question is not about that (ofc. I know reflection doesn't work with unexported field).
It's about Initializing a field which is a map that is nil when the struct get created.

Also, quite often reflection can be replaced with something better.

+ egon