hi ,
I am also having the same problem, can you please elaborate
invalid operation: dat["connections"]["current"] (type interface {} does
not support indexing)
Thanks
On Friday, August 21, 2015 at 4:22:22 PM UTC+5:30, Giulio Iotti wrote:
>
> On Friday, August 21, 2015 at 11:51:32 AM UTC+2, Victor Hooi wrote:
>>
>> [...]
>> However, the following will not work:
>>
>> fmt.Println(dat["connections"]["current"])
>>
>>
>> I get:
>>
>>
>> ./parse_serverstatus.go:37: invalid operation:
>>> dat["connections"]["current"] (type interface {} does not support indexing)
>>
>>
>> The thing is, not every field is nested to to the same depth.
>>
>>
>> Question 1 - Is there a way to unmarshall the above JSON, and have Go
>> "magically" handle the types, and still allow me to access them afterwards
>> as a normal map?
>>
>
> No, there is no magic. But there is a pretty neat syntax, a type switch:
> https://golang.org/doc/effective_go.html#type_switch
>
> So in your case, asset that dat["connections"] is a map; it is, get
> "current", otherwise...
>
>
>> (For context, in Python, I'm just using "server_status_json =
>> json.loads(line)", and it all pretty much works as you'd expect).
>>
>
> Yes, but Python has a different view of types ;)
>
>
>> Question 2 - Is there a way to store a mapping of names, to locations,
>> such that I can access metrics easily?
>>
>>
>> For example, in the Python version I have:
>>
>>
>> def get_nested_items(obj, *names):
>>> """Return obj[name][name2] ... [nameN] for any list of names."""
>>> for name in names:
>>> obj = obj[name]
>>> return obj
>>> metrics_to_extract = {
>>> 'available_connections': ['connections', 'available'],
>>> 'current_connections': ['connections', 'current']
>>> }
>>> for key, names in metrics_to_extract.items():
>>> value = get_nested_items(server_status_json, *names)
>>> json_points.append(create_point(key, value, timestamp, tags))
>>
>>
>> In this case, metrics_to_extract has the name and locations, and I just
>> iterate over that and add them to my output (json_points).
>>
>> (Originally I was using locations like
>> "server_status_json['connections']['current']" along with eval(), which
>> wasn't the best).
>>
>> What's the idiomatic way of doing this in Go?
>>
>
> Wherever you have a map of constant keys in Python, make a struct in Go.
> Then you can have a slice of structs (pointers).
>
>
>> Question 3 - One other complication is that sometimes, some of the float
>> fields get wrapped in a "floatApprox" - e.g.:
>>
>> "connections": {
>>> "current": 131,
>>> "available": 51069,
>>> "totalCreated": {
>>> "floatApprox": 177400
>>> }
>>> },
>>
>>
>> What's a clean way of handling this? Would you just try and access the
>> location, and if it failed, try again but adding one level of floatApprox
>> nesting - does that sound reasonable?
>>
>
> As above, you need type assertions. Ask again if you want examples of more
> clarifications!
>
> --
> Giulio
> https://twitter.com/dullboy
>
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