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Diffstat (limited to 'docs/api-guide/fields.md')
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diff --git a/docs/api-guide/fields.md b/docs/api-guide/fields.md index 914d0861..e05c0306 100644 --- a/docs/api-guide/fields.md +++ b/docs/api-guide/fields.md @@ -2,11 +2,11 @@ # Serializer fields -> Flat is better than nested. +> Each field in a Form class is responsible not only for validating data, but also for "cleaning" it — normalizing it to a consistent format. > -> — [The Zen of Python][cite] +> — [Django documentation][cite] -Serializer fields handle converting between primative values and internal datatypes. They also deal with validating input values, as well as retrieving and setting the values from their parent objects. +Serializer fields handle converting between primitive values and internal datatypes. They also deal with validating input values, as well as retrieving and setting the values from their parent objects. --- @@ -16,7 +16,7 @@ Serializer fields handle converting between primative values and internal dataty ## Core arguments -Each serializer field class constructor takes at least these arguments. Some Field classes take additional, field-specific arguments, but the following should always be accepted: +Each serializer field class constructor takes at least these arguments. Some Field classes take additional, field-specific arguments, but the following should always be accepted: ### `source` @@ -28,7 +28,7 @@ Defaults to the name of the field. ### `read_only` -Set this to `True` to ensure that the field is used when serializing a representation, but is not used when updating an instance dureing deserialization. +Set this to `True` to ensure that the field is used when serializing a representation, but is not used when updating an instance during deserialization. Defaults to `False` @@ -41,7 +41,9 @@ Defaults to `True`. ### `default` -If set, this gives the default value that will be used for the field if none is supplied. If not set the default behaviour is to not populate the attribute at all. +If set, this gives the default value that will be used for the field if no input value is supplied. If not set the default behavior is to not populate the attribute at all. + +May be set to a function or other callable, in which case the value will be evaluated each time it is used. ### `validators` @@ -56,6 +58,13 @@ A dictionary of error codes to error messages. Used only if rendering the field to HTML. This argument sets the widget that should be used to render the field. +### `label` + +A short text string that may be used as the name of the field in HTML form fields or other descriptive elements. + +### `help_text` + +A text string that may be used as a description of the field in HTML form fields or other descriptive elements. --- @@ -69,6 +78,9 @@ A generic, **read-only** field. You can use this field for any attribute that d For example, using the following model. + from django.db import models + from django.utils.timezone import now + class Account(models.Model): owner = models.ForeignKey('auth.user') name = models.CharField(max_length=100) @@ -76,13 +88,14 @@ For example, using the following model. payment_expiry = models.DateTimeField() def has_expired(self): - now = datetime.datetime.now() - return now > self.payment_expiry + return now() > self.payment_expiry A serializer definition that looked like this: + from rest_framework import serializers + class AccountSerializer(serializers.HyperlinkedModelSerializer): - expired = Field(source='has_expired') + expired = serializers.Field(source='has_expired') class Meta: fields = ('url', 'owner', 'name', 'expired') @@ -96,19 +109,38 @@ Would produce output similar to: 'expired': True } -By default, the `Field` class will perform a basic translation of the source value into primative datatypes, falling back to unicode representations of complex datatypes when necessary. +By default, the `Field` class will perform a basic translation of the source value into primitive datatypes, falling back to unicode representations of complex datatypes when necessary. -You can customize this behaviour by overriding the `.to_native(self, value)` method. +You can customize this behavior by overriding the `.to_native(self, value)` method. ## WritableField -A field that supports both read and write operations. By itself `WriteableField` does not perform any translation of input values into a given type. You won't typically use this field directly, but you may want to override it and implement the `.to_native(self, value)` and `.from_native(self, value)` methods. +A field that supports both read and write operations. By itself `WritableField` does not perform any translation of input values into a given type. You won't typically use this field directly, but you may want to override it and implement the `.to_native(self, value)` and `.from_native(self, value)` methods. ## ModelField A generic field that can be tied to any arbitrary model field. The `ModelField` class delegates the task of serialization/deserialization to it's associated model field. This field can be used to create serializer fields for custom model fields, without having to create a new custom serializer field. -**Signature:** `ModelField(model_field=<Django ModelField class>)` +The `ModelField` class is generally intended for internal use, but can be used by your API if needed. In order to properly instantiate a `ModelField`, it must be passed a field that is attached to an instantiated model. For example: `ModelField(model_field=MyModel()._meta.get_field('custom_field'))` + +**Signature:** `ModelField(model_field=<Django ModelField instance>)` + +## SerializerMethodField + +This is a read-only field. It gets its value by calling a method on the serializer class it is attached to. It can be used to add any sort of data to the serialized representation of your object. The field's constructor accepts a single argument, which is the name of the method on the serializer to be called. The method should accept a single argument (in addition to `self`), which is the object being serialized. It should return whatever you want to be included in the serialized representation of the object. For example: + + from django.contrib.auth.models import User + from django.utils.timezone import now + from rest_framework import serializers + + class UserSerializer(serializers.ModelSerializer): + days_since_joined = serializers.SerializerMethodField('get_days_since_joined') + + class Meta: + model = User + + def get_days_since_joined(self, obj): + return (now() - obj.date_joined).days --- @@ -133,7 +165,7 @@ or `django.db.models.fields.TextField`. ## URLField -Corresponds to `django.db.models.fields.URLField`. Uses Django's `django.core.validators.URLValidator` for validation. +Corresponds to `django.db.models.fields.URLField`. Uses Django's `django.core.validators.URLValidator` for validation. **Signature:** `CharField(max_length=200, min_length=None)` @@ -153,11 +185,15 @@ A text representation, validates the text to be a valid e-mail address. Corresponds to `django.db.models.fields.EmailField` -## DateField +## RegexField -A date representation. +A text representation, that validates the given value matches against a certain regular expression. -Corresponds to `django.db.models.fields.DateField` +Uses Django's `django.core.validators.RegexValidator` for validation. + +Corresponds to `django.forms.fields.RegexField` + +**Signature:** `RegexField(regex, max_length=None, min_length=None)` ## DateTimeField @@ -165,184 +201,147 @@ A date and time representation. Corresponds to `django.db.models.fields.DateTimeField` -## IntegerField - -An integer representation. - -Corresponds to `django.db.models.fields.IntegerField`, `django.db.models.fields.SmallIntegerField`, `django.db.models.fields.PositiveIntegerField` and `django.db.models.fields.PositiveSmallIntegerField` - -## FloatField - -A floating point representation. - -Corresponds to `django.db.models.fields.FloatField`. - -## FileField - -A file representation. Performs Django's standard FileField validation. - -Corresponds to `django.forms.fields.FileField`. - -**Signature:** `FileField(max_length=None, allow_empty_file=False)` - - - `max_length` designates the maximum length for the file name. - - - `allow_empty_file` designates if empty files are allowed. - -## ImageField +When using `ModelSerializer` or `HyperlinkedModelSerializer`, note that any model fields with `auto_now=True` or `auto_now_add=True` will use serializer fields that are `read_only=True` by default. -An image representation. +If you want to override this behavior, you'll need to declare the `DateTimeField` explicitly on the serializer. For example: -Corresponds to `django.forms.fields.ImageField`. + class CommentSerializer(serializers.ModelSerializer): + created = serializers.DateTimeField() -Requires the `PIL` package. + class Meta: + model = Comment -Signature and validation is the same as with `FileField`. +Note that by default, datetime representations are determined by the renderer in use, although this can be explicitly overridden as detailed below. ---- +In the case of JSON this means the default datetime representation uses the [ECMA 262 date time string specification][ecma262]. This is a subset of ISO 8601 which uses millisecond precision, and includes the 'Z' suffix for the UTC timezone, for example: `2013-01-29T12:34:56.123Z`. -**Note:** `FileFields` and `ImageFields` are only suitable for use with MultiPartParser, since eg json doesn't support file uploads. -Django's regular [FILE_UPLOAD_HANDLERS] are used for handling uploaded files. +**Signature:** `DateTimeField(format=None, input_formats=None)` ---- +* `format` - A string representing the output format. If not specified, this defaults to `None`, which indicates that Python `datetime` objects should be returned by `to_native`. In this case the datetime encoding will be determined by the renderer. +* `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `DATETIME_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`. -# Relational Fields +DateTime format strings may either be [Python strftime formats][strftime] which explicitly specify the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style datetimes should be used. (eg `'2013-01-29T12:34:56.000000Z'`) -Relational fields are used to represent model relationships. They can be applied to `ForeignKey`, `ManyToManyField` and `OneToOneField` relationships, as well as to reverse relationships, and custom relationships such as `GenericForeignKey`. +## DateField -## RelatedField +A date representation. -This field can be applied to any of the following: +Corresponds to `django.db.models.fields.DateField` -* A `ForeignKey` field. -* A `OneToOneField` field. -* A reverse OneToOne relationship -* Any other "to-one" relationship. +**Signature:** `DateField(format=None, input_formats=None)` -By default `RelatedField` will represent the target of the field using it's `__unicode__` method. +* `format` - A string representing the output format. If not specified, this defaults to `None`, which indicates that Python `date` objects should be returned by `to_native`. In this case the date encoding will be determined by the renderer. +* `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `DATE_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`. -You can customise this behaviour by subclassing `ManyRelatedField`, and overriding the `.to_native(self, value)` method. +Date format strings may either be [Python strftime formats][strftime] which explicitly specify the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style dates should be used. (eg `'2013-01-29'`) -## ManyRelatedField +## TimeField -This field can be applied to any of the following: - -* A `ManyToManyField` field. -* A reverse ManyToMany relationship. -* A reverse ForeignKey relationship -* Any other "to-many" relationship. +A time representation. -By default `ManyRelatedField` will represent the targets of the field using their `__unicode__` method. +Optionally takes `format` as parameter to replace the matching pattern. -For example, given the following models: +Corresponds to `django.db.models.fields.TimeField` - class TaggedItem(models.Model): - """ - Tags arbitrary model instances using a generic relation. - - See: https://docs.djangoproject.com/en/dev/ref/contrib/contenttypes/ - """ - tag = models.SlugField() - content_type = models.ForeignKey(ContentType) - object_id = models.PositiveIntegerField() - content_object = GenericForeignKey('content_type', 'object_id') - - def __unicode__(self): - return self.tag - - - class Bookmark(models.Model): - """ - A bookmark consists of a URL, and 0 or more descriptive tags. - """ - url = models.URLField() - tags = GenericRelation(TaggedItem) - -And a model serializer defined like this: +**Signature:** `TimeField(format=None, input_formats=None)` - class BookmarkSerializer(serializers.ModelSerializer): - tags = serializers.ManyRelatedField(source='tags') - - class Meta: - model = Bookmark - exclude = ('id',) +* `format` - A string representing the output format. If not specified, this defaults to `None`, which indicates that Python `time` objects should be returned by `to_native`. In this case the time encoding will be determined by the renderer. +* `input_formats` - A list of strings representing the input formats which may be used to parse the date. If not specified, the `TIME_INPUT_FORMATS` setting will be used, which defaults to `['iso-8601']`. -Then an example output format for a Bookmark instance would be: - - { - 'tags': [u'django', u'python'], - 'url': u'https://www.djangoproject.com/' - } +Time format strings may either be [Python strftime formats][strftime] which explicitly specify the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style times should be used. (eg `'12:34:56.000000'`) -## PrimaryKeyRelatedField / ManyPrimaryKeyRelatedField +## IntegerField -`PrimaryKeyRelatedField` and `ManyPrimaryKeyRelatedField` will represent the target of the relationship using it's primary key. +An integer representation. -By default these fields are read-write, although you can change this behaviour using the `read_only` flag. +Corresponds to `django.db.models.fields.IntegerField`, `django.db.models.fields.SmallIntegerField`, `django.db.models.fields.PositiveIntegerField` and `django.db.models.fields.PositiveSmallIntegerField` -**Arguments**: +## FloatField -* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. +A floating point representation. -## SlugRelatedField / ManySlugRelatedField +Corresponds to `django.db.models.fields.FloatField`. -`SlugRelatedField` and `ManySlugRelatedField` will represent the target of the relationship using a unique slug. +## DecimalField -By default these fields read-write, although you can change this behaviour using the `read_only` flag. +A decimal representation. -**Arguments**: +Corresponds to `django.db.models.fields.DecimalField`. -* `slug_field` - The field on the target that should be used to represent it. This should be a field that uniquely identifies any given instance. For example, `username`. -* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. +## FileField -## HyperlinkedRelatedField / ManyHyperlinkedRelatedField +A file representation. Performs Django's standard FileField validation. -`HyperlinkedRelatedField` and `ManyHyperlinkedRelatedField` will represent the target of the relationship using a hyperlink. +Corresponds to `django.forms.fields.FileField`. -By default, `HyperlinkedRelatedField` is read-write, although you can change this behaviour using the `read_only` flag. +**Signature:** `FileField(max_length=None, allow_empty_file=False)` -**Arguments**: + - `max_length` designates the maximum length for the file name. + + - `allow_empty_file` designates if empty files are allowed. -* `view_name` - The view name that should be used as the target of the relationship. **required**. -* `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument. -* `queryset` - By default `ModelSerializer` classes will use the default queryset for the relationship. `Serializer` classes must either set a queryset explicitly, or set `read_only=True`. -* `slug_field` - The field on the target that should be used for the lookup. Default is `'slug'`. -* `pk_url_kwarg` - The named url parameter for the pk field lookup. Default is `pk`. -* `slug_url_kwarg` - The named url parameter for the slug field lookup. Default is to use the same value as given for `slug_field`. +## ImageField -## HyperLinkedIdentityField +An image representation. -This field can be applied as an identity relationship, such as the `'url'` field on a HyperlinkedModelSerializer. +Corresponds to `django.forms.fields.ImageField`. -This field is always read-only. +Requires either the `Pillow` package or `PIL` package. The `Pillow` package is recommended, as `PIL` is no longer actively maintained. -**Arguments**: +Signature and validation is the same as with `FileField`. -* `view_name` - The view name that should be used as the target of the relationship. **required**. -* `format` - If using format suffixes, hyperlinked fields will use the same format suffix for the target unless overridden by using the `format` argument. -* `slug_field` - The field on the target that should be used for the lookup. Default is `'slug'`. -* `pk_url_kwarg` - The named url parameter for the pk field lookup. Default is `pk`. -* `slug_url_kwarg` - The named url parameter for the slug field lookup. Default is to use the same value as given for `slug_field`. +--- -# Other Fields +**Note:** `FileFields` and `ImageFields` are only suitable for use with MultiPartParser, since e.g. json doesn't support file uploads. +Django's regular [FILE_UPLOAD_HANDLERS] are used for handling uploaded files. -## SerializerMethodField +--- -This is a read-only field. It gets its value by calling a method on the serializer class it is attached to. It can be used to add any sort of data to the serialized representation of your object. The field's constructor accepts a single argument, which is the name of the method on the serializer to be called. The method should accept a single argument (in addition to `self`), which is the object being serialized. It should return whatever you want to be included in the serialized representation of the object. For example: +# Custom fields - from rest_framework import serializers - from django.contrib.auth.models import User - from django.utils.timezone import now +If you want to create a custom field, you'll probably want to override either one or both of the `.to_native()` and `.from_native()` methods. These two methods are used to convert between the initial datatype, and a primitive, serializable datatype. Primitive datatypes may be any of a number, string, date/time/datetime or None. They may also be any list or dictionary like object that only contains other primitive objects. - class UserSerializer(serializers.ModelSerializer): +The `.to_native()` method is called to convert the initial datatype into a primitive, serializable datatype. The `from_native()` method is called to restore a primitive datatype into it's initial representation. - days_since_joined = serializers.SerializerMethodField('get_days_since_joined') +## Examples - class Meta: - model = User +Let's look at an example of serializing a class that represents an RGB color value: - def get_days_since_joined(self, obj): - return (now() - obj.date_joined).days + class Color(object): + """ + A color represented in the RGB colorspace. + """ + def __init__(self, red, green, blue): + assert(red >= 0 and green >= 0 and blue >= 0) + assert(red < 256 and green < 256 and blue < 256) + self.red, self.green, self.blue = red, green, blue -[cite]: http://www.python.org/dev/peps/pep-0020/ + class ColourField(serializers.WritableField): + """ + Color objects are serialized into "rgb(#, #, #)" notation. + """ + def to_native(self, obj): + return "rgb(%d, %d, %d)" % (obj.red, obj.green, obj.blue) + + def from_native(self, data): + data = data.strip('rgb(').rstrip(')') + red, green, blue = [int(col) for col in data.split(',')] + return Color(red, green, blue) + + +By default field values are treated as mapping to an attribute on the object. If you need to customize how the field value is accessed and set you need to override `.field_to_native()` and/or `.field_from_native()`. + +As an example, let's create a field that can be used represent the class name of the object being serialized: + + class ClassNameField(serializers.Field): + def field_to_native(self, obj, field_name): + """ + Serialize the object's class name. + """ + return obj.__class__ + +[cite]: https://docs.djangoproject.com/en/dev/ref/forms/api/#django.forms.Form.cleaned_data [FILE_UPLOAD_HANDLERS]: https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-FILE_UPLOAD_HANDLERS +[ecma262]: http://ecma-international.org/ecma-262/5.1/#sec-15.9.1.15 +[strftime]: http://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior +[iso8601]: http://www.w3.org/TR/NOTE-datetime |