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Diffstat (limited to 'docs/api-guide')
| -rw-r--r-- | docs/api-guide/serializers.md | 29 |
1 files changed, 22 insertions, 7 deletions
diff --git a/docs/api-guide/serializers.md b/docs/api-guide/serializers.md index c88b9b0c..ee7f72dd 100644 --- a/docs/api-guide/serializers.md +++ b/docs/api-guide/serializers.md @@ -47,7 +47,7 @@ The first part of serializer class defines the fields that get serialized/deseri We can now use `CommentSerializer` to serialize a comment, or list of comments. Again, using the `Serializer` class looks a lot like using a `Form` class. - serializer = CommentSerializer(instance=comment) + serializer = CommentSerializer(comment) serializer.data # {'email': u'leila@example.com', 'content': u'foo bar', 'created': datetime.datetime(2012, 8, 22, 16, 20, 9, 822774)} @@ -65,20 +65,29 @@ Deserialization is similar. First we parse a stream into python native datatype ...then we restore those native datatypes into a fully populated object instance. - serializer = CommentSerializer(data) + serializer = CommentSerializer(data=data) serializer.is_valid() # True serializer.object # <Comment object at 0x10633b2d0> >>> serializer.deserialize('json', stream) +When deserializing data, we can either create a new instance, or update an existing instance. + + serializer = CommentSerializer(data=data) # Create new instance + serializer = CommentSerializer(comment, data=data) # Update `instance` + ## Validation When deserializing data, you always need to call `is_valid()` before attempting to access the deserialized object. If any validation errors occur, the `.errors` and `.non_field_errors` properties will contain the resulting error messages. ### Field-level validation -You can specify custom field-level validation by adding `validate_<fieldname>()` methods to your `Serializer` subclass. These are analagous to `clean_<fieldname>` methods on Django forms, but accept slightly different arguments. They take a dictionary of deserialized attributes as a first argument, and the field name in that dictionary as a second argument (which will be either the name of the field or the value of the `source` argument to the field, if one was provided). Your `validate_<fieldname>` methods should either just return the attrs dictionary or raise a `ValidationError`. For example: +You can specify custom field-level validation by adding `.validate_<fieldname>` methods to your `Serializer` subclass. These are analagous to `.clean_<fieldname>` methods on Django forms, but accept slightly different arguments. + +They take a dictionary of deserialized attributes as a first argument, and the field name in that dictionary as a second argument (which will be either the name of the field or the value of the `source` argument to the field, if one was provided). + +Your `validate_<fieldname>` methods should either just return the `attrs` dictionary or raise a `ValidationError`. For example: from rest_framework import serializers @@ -88,16 +97,22 @@ You can specify custom field-level validation by adding `validate_<fieldname>()` def validate_title(self, attrs, source): """ - Check that the blog post is about Django + Check that the blog post is about Django. """ value = attrs[source] - if "Django" not in value: + if "django" not in value.lower(): raise serializers.ValidationError("Blog post is not about Django") return attrs -### Final cross-field validation +### Object-level validation + +To do any other validation that requires access to multiple fields, add a method called `.validate()` to your `Serializer` subclass. This method takes a single argument, which is the `attrs` dictionary. It should raise a `ValidationError` if necessary, or just return `attrs`. + +## Saving object state + +Serializers also include a `.save()` method that you can override if you want to provide a method of persisting the state of a deserialized object. The default behavior of the method is to simply call `.save()` on the deserialized object instance. -To do any other validation that requires access to multiple fields, add a method called `validate` to your `Serializer` subclass. This method takes a single argument, which is the `attrs` dictionary. It should raise a `ValidationError` if necessary, or just return `attrs`. +The generic views provided by REST framework call the `.save()` method when updating or creating entities. ## Dealing with nested objects |