[erlang-questions] Querying JSON, team chat

Seth Falcon seth@REDACTED
Sun Apr 7 17:58:09 CEST 2013

(hope you don't mind that I put this back on the list)

On Sat, Apr 6, 2013 at 11:04 PM, Andrei Soroker <soroker@REDACTED> wrote:

> Whoa, I had no idea ej existed! Why did you pick a tuple vs. a list for
> the path?

To be honest, I don't think this was a very good design choice on my part
and I would go with a list if I was starting over. I wanted to be able to
support accessing array elements by index and if I'm remembering my thought
process, I was worried about the ambiguity of passing a bare string
accidentally instead of a list. In ej, you can do:

J = [<<"a1">>, <<"a2">>, <<"a3">>].
ej:get({2}, J).


If the path argument was a list, and bare integers were still the way to
ask for an array element by index, then the code would allow you to say

ej:get("accident", J)

That would probably end up failing anyway, just not straight away. Given
how infrequently I've ended up with a need for array access by index, I
think a better choice would have been to stick with list for the path and
then tag indices like {idx, 5}.

> I am also somewhat partial to the analogy with XPath, which only addresses
> reading and not writing.

Horses for courses :) We end up using the set and delete quite a bit for
normalizing incoming data before validating with ej:valid.

+ seth

Seth Falcon | @sfalcon | http://userprimary.net/
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