Unmarshalling Json with fields with underscores in their names

[Magnús Örn Gylfason]

Hi

Im parsing a JSON string (the post from GitHubs WebHooks) into a data structure and every json field that has an underscore in the name is returned with zero value. This applies to bools (to false), ints (to 0) and structures (which become uninitialized). Everything else is parsed.

Im using tags (e.g. "`json:pushed_at`") to name all fields.

Is this known behaviour?

cheers,

mg

[Andy R]

Put quotes around "pushed_at"

http://play.golang.org/p/PfS1Y6KvmH

[minux]

On Tue, Sep 24, 2013 at 5:12 PM, Magnús Örn Gylfason <magnus....@gmail.com> wrote:

Hi

Im parsing a JSON string (the post from GitHubs WebHooks) into a data structure and every json field that has an underscore in the name is returned with zero value. This applies to bools (to false), ints (to 0) and structures (which become uninitialized). Everything else is parsed.

the "_" character is treated as a lower case character, so those fields are private and json decoder can't

assign to them. 

Im using tags (e.g. "`json:pushed_at`") to name all fields.

Is this known behaviour?

cheers,

mg

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[Andrew Gerrand]

Do your struct field names begin with capital letters? If not, encoding/json can't see them.

Your structs should look something like this:

  type Object struct {

    PushedAt string `json:"pushed_at"`

  }

Andrew

--

[Magnús Örn Gylfason]

The way I was doing this was:

PushedAt     int64  `json:pushed_at`

Adding the extra " as you suggested did the trick:

PushedAt     int64  `json:"pushed_at"`

Why this is need for fields with _ I don't understand, e.g. this works:

Size         int64  `json:size`

Seems the " is only needed when a _ is in the json field name.

Thank you both.

[Matthew Kane]

Because the encoding/json package will also consider a case
insensitive match if no tagged struct with an exact match is present.

On Wed, Sep 25, 2013 at 2:47 PM, Magnús Örn Gylfason

--
matt kane
twitter: the_real_mkb / nynexrepublic
http://hydrogenproject.com

[Andy R]

You're just lucky that is works without the " for simple names. The reflect package (which is used by json pkg) clearly specifies:


http://golang.org/pkg/reflect/#StructTag

"Each value is quoted using U+0022 '"' characters and Go string literal syntax."

Also the json package states you have to use quotes:

http://golang.org/pkg/encoding/json/#Marshal

You'll never know what happens in the future, this might break so I'd suggest enclosing all field names with quotes to be safe.

Cheers

[Camilo Aguilar]

I also found that it doesn't like a space between the colon and the double quotes: 

This didn't unmarshal properly for me: `json: "my_name"` 

Changing it to `json:"my_name"` made it work. It is sad the fragility of this.

[Ingo Oeser]

Please note that "go vet" would have found this for you.

So at least you have a chance to catch this issue in a pre-commit hook or CI system before you go into production.