Unmarshaling a JSON decimal optionally represented as a string

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1

Hi forum,
I’m writing a client for an API that is somewhat broken.
It would sometimes return decimal numbers and other times return the numbers represented as strings from the same endpoints. Since I can’t get the api owners to fix it (I wonder how their own client works…), I’ve fixed the problem in the following way:

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

I don’t think it’s the correct way, since I would have to write an UnmarshalJSON method for every endpoint. It seems to me there must be a better way? I was thinking of writing a custom struct tag like the json:",string" called “stringoptional”, but I have no idea where to start and if it’s the correct place to solve my problem.

Any ideas?

2

I think the most usual option would be to use an empty interface and reflection… unless I’m missing something and that doesn’t address your particular problem.

3

json.Number may solve this for you almost automatically:

1 Like
4

Ok, json.Number eliminates the custom type and my inefficient unmarshaling in there, so it’s better. Thank you!
I would still have to write UnmarshalJSON methods for all structs (code that uses this client should not know anything about json.) and it’s a lot of structs. If there’s nothing else I can improve maybe go generate can help with that.

5

Thanks for the reply. Using an empty interface and type checking the value inside every struct.UnmarshalJSON() might be more efficient than my custom type, but I still think that is not the right place to solve this problem. If I have to go that route I will use @calmh 's suggestion and code generate, but I hope there’s another way.

6

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