How to store a struct inside a struct in go?

Question

I have two structure (New and DailyPrediction) with DailyPrediction structure as one of the entity of New structure:

type New struct {
    Id string
    DailyPrediction
}

type DailyPrediction struct {
    Prediction string
}

I am unable to read (or) write the structure new in the datastore. It would be helpful if someone can help me on this.

Datastore? An App Engine datastore maybe? If so it would help to tag the question google-app-engine or gae-datastore. — Sonia
– Sonia, Commented Dec 7, 2012 at 16:07
I removed the app-engine tag as the question does not seem to be related to app engine directly. Maybe I misread the question? — matthias krull
– matthias krull, Commented Dec 7, 2012 at 16:16

Derek · Accepted Answer · 2012-12-07 18:49:38Z

1

It is unclear to me from your question what exactly you are doing with the struct, and in what way it is failing. However, while you are embedding the DailyPrediction struct in your new struct by not giving it a name, it still needs to be initialized. You can see details of how to do that here: http://golang.org/doc/effective_go.html#embedding

For example, in order to initialize your New struct, you may use a line like this:

    n := New{"foo", DailyPrediction{"bar"}}

Could that be what was missing?

answered Dec 7, 2012 at 18:49

Derek

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3 Comments

Raj Over a year ago

Thanks a lot...I wasn't clear in the question i posted. I am actually creating this structure to create a Json and save it in datastore. The Json structure should be like this {"Id":"20122403","Dailypred":{"Prediction":"ABCD"}}. The problem while reading the Json is that it throws an error - "SAVE datastore: unsupported struct field type: pcg_new.DailyPrediction"..please help on this

Derek Over a year ago

I just did the following: var jsonBlob = []byte({"Id": "meemaw", "Prediction": "Moonpie"}), and that successfully unmarshalled to the struct I made, where the DailyPrediction struct contains the string Prediction. Is that what you're looking for?

Derek Over a year ago

Never mind, I see that the problem wasn't getting json to read it, but appEngine to store it. It sounds like the answer by @alphazero is more relevant, that this is not supported.

alphazero · Accepted Answer · 2012-12-07 19:25:10Z

1

Not supported by the appengine.

answered Dec 7, 2012 at 19:25

alphazero

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1 Comment

Ali Over a year ago

It is supported by the app engine, in the sense that you can do it yourself, the libraries don't take care of it. You need to implement the interface and flatten things out.

Dewey · Accepted Answer · 2018-12-02 02:14:21Z

0

Just to update this post for future readers ... this info is OLD ... nested structs are now supported

answered Dec 2, 2018 at 2:14

Dewey

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