Define modules struct in main go

[RoboTamer]

How do I use a struct that has been defined in the main application, in a module / library.

I am keep getting this error:

../gotamer/cfg/cfg.go:24: undefined: JsonCfg

// main.go

package main

import (

"gotamer/cfg"

"gotamer/e"

)

var Cfg JsonCfg

type JsonCfg struct{

Appl       string

Hostname   string

ListenAddr string

IpAddr     string

Debug      uint

}

func main() {

c, ok := cfg.Get(Cfg)

e.Fail(ok)

}

// cfg.go

package cfg

import (

"encoding/json"

"io/ioutil"

)

const file = "cfg.json" 

 

func Get(c *JsonCfg) (b []byte, ok error) {

b, ok = ioutil.ReadFile(file)

if ok != nil {

put() // Generates a template json file

return c, ok

}

ok = json.Unmarshal(b, &c)

if ok != nil {

println("Bad json File: ", ok)

}

return b, ok

}

[Mike Rosset]

assuming you used cfg for you package name then 

var cfg cfg.JsonCfg

[RoboTamer]

Tried that one already, doesn't work

[Mike Rosset]

I replied to fast sorry. I dont think this will work. not in this order anyways.

since package cfg does not know what JsonCfg is.

[DisposaBoy]

On Saturday, September 8, 2012 8:55:30 AM UTC+1, RoboTamer wrote:

How do I use a struct that has been defined in the main application, in a module / library.

I am keep getting this error:

../gotamer/cfg/cfg.go:24: undefined: JsonCfg

 [..]

I assume by module/library you mean package? in that case, if JsonCfg is defined in another package then you need to import that package. In this case that other package is main which you can't import so your only option is to defined that type somewhere  that allows you to import it. From the sounds of it that JsonCfg should actually be in whatever package cfg.go is in then your main package can import that package to access the type.

[Mike Rosset]

On Sat, Sep 8, 2012 at 12:55 AM, RoboTamer <grue...@gmail.com> wrote:

in this case I would use a function, and pass interface. basically your config struct.

see

https://github.com/str1ngs/util/blob/master/json/json.go#L72

[RoboTamer]

The thing is, I like the cfg.go package to be independent.

Meaning that is going to be a package on bitbucket or github

So the JsonCfg struct need to be defined outside of this package.

If I understand you right I need to create a 3rd package and just place the JsonCfg Struct in there?

That sucks, but I'll try it  

[Mike Rosset]

no you do not need another package if you pass your struct as interface{}

[RoboTamer]

Thank you, interface works!

interfaces to me are still magic, I can't wrap my head around them.

Do you know of a simple reading, that explains that to me.

Nothing I read so far makes total sense to me.   

[Mike Rosset]

http://golang.org/doc/effective_go.html

has abit about interfaces

http://golang.org/ref/spec#Interface_types explains interface{}

[RoboTamer]

Again thanks for your help.

Here is the result:

Enjoy, and let me know of any possible improvements or bugs

https://bitbucket.org/gotamer/cfg

[Mike Rosset]

Think your bitbucket repo is read only.

[Mike Rosset]

sorry ment private

[RoboTamer]

Sorry about that, it's the default at bitbucket 

Works now, here are the docs:

http://go.pkgdoc.org/bitbucket.org/gotamer/cfg

[Mike Rosset]

Looks good, only thing I might suggest is not using ok for error. ok generally is used for bool, and err for error.

[RoboTamer]

On Saturday, September 8, 2012 3:51:07 AM UTC-7, Mike Rosset wrote:

Looks good, only thing I might suggest is not using ok for error. ok generally is used for bool, and err for error.

I didn't know about that convention, I updated the package, thanks