Re: [go-nuts] xml Unmarshal does not see expected type

[Jakob Borg]

You are setting an interface to a struct value, then passing Unmarshal a 
pointer to the interface. This is the wrong “order” of pointers and will result 
in Unmarshal overwriting the pointed to interface with the map. What you want 
to do is pass Unmarshal a pointer to your struct type:

var x X{}
err := xml.Unmarshal(data, &x)

or, equivalently via an interface:

var x X{}
var intf interface{} = &x
err := xml.Unmarshal(data, intf)

This boxing is exactly the same thing that happens automatically in the first 
function call.

//jb


On 16 Nov 2017, at 21:52, Diego Medina 
<fmpwiz...@gmail.com<mailto:fmpwiz...@gmail.com>> wrote:

Hi,

At work I have 3 different xml files I need to parse (different fields each), 
Because going from the xml bytes into a struct is pretty much the same
for all 3 types, I thought I could do something like


var payload interface{}

if kind == "A" {
  paylaod = TypeA{}
}


if kind == "B" {
  paylaod = TypeB{}
}


if kind == "C" {
  paylaod = TypeC{}
}

....

xml.Unmarshal([]byte(file), &payload)

but this fails. It doesn't give me an error, but Unmarshal doesn't recognize 
the payload variable as the right (new) type.

I created a very simple snippet here

https://play.golang.org/p/QvVbM--Zdt

produces:

gen is type: main.X //<== see how the type is correct here
xml gen is {One:}
json gen is map[One:uno]
gen is type: main.X //<== here I declared the variable with the right type and 
Unmarshal works
xml gen is {One:uno}
json gen is {One:uno}

Hope this is enough information.

Thanks

Diego

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