Marc,
> On 24 May 2017, at 16:20, Marc Hanisch via Pharo-users
> <pharo-users@lists.pharo.org> wrote:
> Hello,
>
> is there a way to query a JSON with a path (JSONPath or some custom format)?
>
> I want to query an API and collect the JSON responses, which I need to
> iterate over to extract some data. Modelling the JSON structure as classes
> would be too much overhead, I think. I just want to collect some values...
>
> Thanks in advance,
> Marc
Normally, when you use the NeoJSON package and you don't do any mapping, you
get Dictionaries and Arrays back.
There is however also something called NeoJSONObject, a Dictionary subclass
that has some API that is quite fluent and that does include path style access.
To get started, use NeoJSONObject class>>#fromString: as parser.
Here is the class comment:
===
I am NeoJSONObject.
I am a Dictionary.
I behave more like a JavaScript object. I return nil for missing keys. I allow
any property to be read or set by using a normal accessor message.
The following are equivalent:
self foo.
self at: #foo.
As are the following
self foo: 1.
self at: #foo put: 1.
Except that in the first case, self is returned.
I can optionally be used by NeoJSONReader as mapClass (see #mapClass:).
For output, I act just like my superclass (it is thus not necessary to do any
conversions).
Example:
NeoJSONObject fromString: '{"foo":1,"bar":-2}'.
NeoJSONObject new foo: 1; bar: -2.
{ #x -> 100. #y -> 200 } as: NeoJSONObject.
(NeoJSONObject new data: (NeoJSONObject new id: #sensor1; value: 37.5))
asString.
I use JSON as my printed representation. To convert me to JSON, use
#printString or #asString.
Additionally, I support path access for nested instances of me, using #atPath:
and #atPath:put:
The first is special because it returns nil as soon as a key is missing. The
second is special because it creates extra levels (instances of me) as needed
to follow the path of keys.
NeoJSONObject new atPath: #(one two three) put: 42; yourself.
NeoJSONObject new atPath: #(one two three) put: 42; atPath: #(one two
three).
===
HTH,
Sven
