# Serializer fields > Flat is better than nested. > > — [The Zen of Python][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. --- **Note:** The serializer fields are declared in fields.py, but by convention you should import them using `from rest_framework import serializers` and refer to fields as `serializers.`. --- # Generic Fields These generic fields are used for representing arbitrary model fields or the output of model methods. ## Field A generic, **read-only** field. You can use this field for any attribute that does not need to support write operations. For example, using the following model. class Account(models.Model): owner = models.ForeignKey('auth.user') name = models.CharField(max_length=100) created = models.DateTimeField(auto_now_add=True) payment_expiry = models.DateTimeField() def has_expired(self): now = datetime.datetime.now() return now > self.payment_expiry A serializer definition that looked like this: class AccountSerializer(serializers.HyperlinkedModelSerializer): expired = Field(source='has_expired') class Meta: fields = ('url', 'owner', 'name', 'expired') Would produce output similar to: { 'url': 'http://example.com/api/accounts/3/', 'owner': 'http://example.com/api/users/12/', 'name': 'FooCorp business account', '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. You can customize this behaviour 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. ## 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=)` --- # Typed Fields These fields represent basic datatypes, and support both reading and writing values. ## BooleanField A Boolean representation. Corresponds to `django.db.models.fields.BooleanField`. ## CharField A text representation, optionally validates the text to be shorter than `max_length` and longer than `min_length`. Corresponds to `django.db.models.fields.CharField` or `django.db.models.fields.TextField`. **Signature:** `CharField(max_length=None, min_length=None)` ## ChoiceField A field that can accept a value out of a limited set of choices. ## EmailField A text representation, validates the text to be a valid e-mail address. Corresponds to `django.db.models.fields.EmailField` ## DateField A date representation. Corresponds to `django.db.models.fields.DateField` ## DateTimeField 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`. --- # Relational Fields 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`. ## RelatedField This field can be applied to any of the following: * A `ForeignKey` field. * A `OneToOneField` field. * A reverse OneToOne relationship * Any other "to-one" relationship. By default `RelatedField` will represent the target of the field using it's `__unicode__` method. You can customise this behaviour by subclassing `ManyRelatedField`, and overriding the `.to_native(self, value)` method. ## ManyRelatedField 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. By default `ManyRelatedField` will represent the targets of the field using their `__unicode__` method. For example, given the following models: 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: class BookmarkSerializer(serializers.ModelSerializer): tags = serializers.ManyRelatedField(source='tags') class Meta: model = Bookmark exclude = ('id',) Then an example output format for a Bookmark instance would be: { 'tags': [u'django', u'python'], 'url': u'https://www.djangoproject.com/' } ## PrimaryKeyRelatedField As with `RelatedField` field can be applied to any "to-one" relationship, such as a `ForeignKey` field. `PrimaryKeyRelatedField` will represent the target of the field using it's primary key. Be default, `PrimaryKeyRelatedField` is read-write, although you can change this behaviour using the `readonly` flag. ## ManyPrimaryKeyRelatedField As with `RelatedField` field can be applied to any "to-many" relationship, such as a `ManyToManyField` field, or a reverse `ForeignKey` relationship. `PrimaryKeyRelatedField` will represent the target of the field using their primary key. Be default, `ManyPrimaryKeyRelatedField` is read-write, although you can change this behaviour using the `readonly` flag. ## HyperlinkedRelatedField ## ManyHyperlinkedRelatedField ## HyperLinkedIdentityField [cite]: http://www.python.org/dev/peps/pep-0020/ #n122'>122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395