How to validate JSON Schema in Objective-C?

Question

I have JSON returned from a server, and I would like to validate it against a JSON Schema (probably draft V3, can change though).

I thought that perhaps NSDictionary would have the functionality, but it doesn't seem to, here is my attempt:

[self.dictionary ]

(where dictionary is an NSDictionary)

There weren't any methods for validating the NSDictionary against a JSON schema that I could find. How do I do this?

Please note that you can write C and C++ in objective-c, hence these tags being present in the question.

I know of no in built way to do this, perhaps there is a third party solution but my guess would be you will have to write it yourself — Simon McLoughlin, Dec 13 '13 at 13:32
You might have tried edit your closed question to get it reopened. — bummi, Dec 13 '13 at 13:35
`JSON returned from a server, and I would like to validate it against a JSON Schema` note, not all JSON objects are dictionaries. — ilya n., Dec 13 '13 at 14:05

score 6 · Answer 1 · answered Dec 13 '13 at 13:52

6

Objective-C is a superset of C. JSON Schema site lists a C library wjelement, you can adapt it.

The example function call is

WJESchemaValidate(schema, json, schema_error, schema_load, NULL, format)

You'll need to supply a C string, rather than NSString, naturally.

Note: after I wrote the answer, I realised you were fine with pure C from the start :)

answered Dec 13 '13 at 13:52

ilya n.

yes, people kept removing my C tag and I'm not allowed to imply you suggest a C library (or my question will be removed. – Sam Dec 13 '13 at 13:55
Looks good, although not the neatest, as I'll have to munge my NSDictionary back to a string then to a C-string, but it does looks like a very mature library, so it should hopefully be worth it. Thanks – Sam Dec 13 '13 at 13:56
1

@Sam, it's better to use just `c` tag, then. – ilya n. Dec 13 '13 at 13:56
didn't want to open 3 questions ;) – Sam Dec 13 '13 at 14:00
Update: seems to be working! thanks. I think I may start work on a pure obj-c version at some point... – Sam Dec 13 '13 at 15:50
just finished and released v0.1 - it currently passes the JSON schema test suite. hope it's useful. – Sam Mar 06 '14 at 14:37

score 4 · Accepted Answer · answered Mar 06 '14 at 14:39

After not finding a satisfactory answer to this question - I went away and developed my own schema validator in native Objective-c here: https://github.com/samskiter/KiteJSONValidator

I've just got it passing all the tests in the JSON-Schema test suite so I've released v0.1.

It's released under the MIT license so I hope it's useful to someone...

score 1 · Answer 3 · answered Jan 29 '14 at 12:51

1

For anyone who is looking for an MIT licensed JSON schema validator, "JsonSchemaValidator" does a nice job and is available here: https://bitbucket.org/nut_code_monkey/jsonschemavalidator

answered Jan 29 '14 at 12:51

jondring

this is good, but doesn't look like it can parse a schema file, as defined by the JSON-Schema spec. It's a nice way of approaching the problem though, as it has typed and validated description language. – Sam Jan 29 '14 at 16:05

3 Answers3