Decoding JSON in golang

May 30th, 2014

When writting some Go code that require testing I meet some weird error (but not bug). Since this error bug me more than once, I figure it would be useful to document this error 

package main

import(
    "fmt"
    "encoding/json"
)

func main() {
    jsonmsg := []byte(`{"item1":"1", "item2":"2"}`)
    // it is important to note that variable in struct must be capital letter ]
    // so that Unmarshall able to parse them properly
    type msg struct{
        Item1 string
        Item2 string
    }
    
    var m msg
    _ = json.Unmarshal(jsonmsg, &m)
    fmt.Println(m)


    // fail example 
    type msgs struct{
        item1 string
        item2 string
    }
    
    var m2 msgs
    _ = json.Unmarshal(jsonmsg, &m2)
    fmt.Println(m2)
}

// output :
//{1 2}
//{ }

Play Ground Example

The reason Example 1 word are because as explained in GoTutorial
if the first letter is capital, it is visible outside the package. That’s it.

So the reason is that simple.

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