diff --git a/docs/faq.rst b/docs/faq.rst index 7495cdb..c24bd8f 100644 --- a/docs/faq.rst +++ b/docs/faq.rst @@ -19,7 +19,9 @@ would pass validation the first time, but fail the second! Still, filling in defaults is a thing that is useful. :mod:`jsonschema` allows you to :doc:`define your own validator classes and callables `, so you can easily create a :class:`IValidator` that does do -default setting. Here's some code to get you started: +default setting. Here's some code to get you started. (In this code, we add +the default properties to each object *before* the properties are validated, +so the default values themselves will need to be valid under the schema.) .. code-block:: python @@ -30,15 +32,15 @@ default setting. Here's some code to get you started: validate_properties = validator_class.VALIDATORS["properties"] def set_defaults(validator, properties, instance, schema): + for property, subschema in properties.iteritems(): + if "default" in subschema: + instance.setdefault(property, subschema["default"]) + for error in validate_properties( validator, properties, instance, schema, ): yield error - for property, subschema in properties.iteritems(): - if "default" in subschema: - instance.setdefault(property, subschema["default"]) - return validators.extend( validator_class, {"properties" : set_defaults}, ) @@ -60,10 +62,50 @@ See the above-linked document for more info on how this works, but basically, it just extends the :validator:`properties` validator on a :class:`Draft4Validator` to then go ahead and update all the defaults. -If you're interested in a more interesting solution to a larger class of these -types of transformations, keep an eye on `Seep -`_, which is an experimental data -transformation and extraction library written on top of :mod:`jsonschema`. +.. note:: + + If you're interested in a more interesting solution to a larger class of these + types of transformations, keep an eye on `Seep + `_, which is an experimental data + transformation and extraction library written on top of :mod:`jsonschema`. + + +.. hint:: + + The above code can provide default values for an entire object and all of its properties, + but only if your schema provides a default value for the object itself, like so: + + .. code-block:: python + + schema = { + "type": "object", + "properties": { + "outer-object": { + "type": "object", + "properties" : { + "inner-object": { + "type": "string", + "default": "INNER-DEFAULT" + } + }, + "default": {} # <-- MUST PROVIDE DEFAULT OBJECT + } + } + } + + obj = {} + DefaultValidatingDraft4Validator(schema).validate(obj) + assert obj == {'outer-object': {'inner-object': 'INNER-DEFAULT'}} + + ...but if you don't provide a default value for your object, + then it won't be instantiated at all, much less populated with default properties. + + .. code-block:: python + + del schema["properties"]["outer-object"]["default"] + obj2 = {} + DefaultValidatingDraft4Validator(schema).validate(obj2) + assert obj2 == {} # whoops How do jsonschema version numbers work?