Possibly also useful if you're dealing with JSON documents with different
structures:
https://github.com/twpayne/go-jsonstruct
This will generate the most specific Go struct possible that covers all the
example documents that you give it. In your example it will generate:
package main
type T struct {
Cities []string `json:"Cities,omitempty"`
Version string `json:"Version"`
Villages []string `json:"Villages,omitempty"`
}
which is the union of all versions.
If you already know exactly what structures you will receive, then Manilo's
approach of first decoding into a struct only the Version field is better
though, especially when combined with Go's runtime type switches.
Regards,
Tom
On Wednesday, April 29, 2020 at 9:31:00 AM UTC+1, Chris Burkert wrote:
>
> That sounds like a good plan. I'm going to try that. Thank you Manlio!
>
> Am Di., 28. Apr. 2020 um 15:11 Uhr schrieb Manlio Perillo <
> [email protected] <javascript:>>:
>
>> On Tuesday, April 28, 2020 at 10:52:56 AM UTC+2, Chris Burkert wrote:
>>>
>>> Dear all,
>>>
>>> my application users shall be able to provide multiple json documents
>>> (files and urls) which I'd like to marshall into one structure.
>>> Additionally these json documents may have different versions. I know how
>>> to marshal a document into a version specific struct if I know the format
>>> version before (for simplicity of this example I don't handle errors):
>>> https://play.golang.org/p/ixVI5CzPqFP
>>>
>>> What I would like (in the example the village field was renamed to
>>> cities ) is a struct of type ModelV2 with all four values merged in Cities.
>>>
>>> Is there a best practice for a backwards compatible behavior which:
>>>
>>> - identifies the json format version of each document
>>> - skips that document if it is higher than the supported format
>>> version in my application
>>> - merges supported format versions into ONE struct
>>>
>>> Of course I have to implement the semantics on my own but how can I
>>> approach the topic?
>>>
>>>
>> You can first unmarshal a struct containing only the Version field. As
>> an example:
>> https://play.golang.org/p/1oDzdWlTCfC
>> <https://play.golang.org/p/6G9ooLneADX>
>>
>>
>> Manlio
>>
>>> thanks
>>>
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