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Diffstat (limited to 'docs/api-guide/fields.md')
| -rw-r--r-- | docs/api-guide/fields.md | 56 |
1 files changed, 52 insertions, 4 deletions
diff --git a/docs/api-guide/fields.md b/docs/api-guide/fields.md index 9a745cf1..42f89f46 100644 --- a/docs/api-guide/fields.md +++ b/docs/api-guide/fields.md @@ -197,12 +197,16 @@ If you want to override this behavior, you'll need to declare the `DateTimeField class Meta: model = Comment +Note that by default, datetime representations are deteremined 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`. + **Signature:** `DateTimeField(format=None, input_formats=None)` -* `format` - A string representing the output format. If not specified, the `DATETIME_FORMAT` setting will be used, which defaults to `'iso-8601'`. +* `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']`. -DateTime format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style datetimes should be used. (eg `'2013-01-29T12:34:56.000000'`) +DateTime format strings may either be [python strftime formats][strftime] which explicitly specifiy 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'`) ## DateField @@ -212,7 +216,7 @@ Corresponds to `django.db.models.fields.DateField` **Signature:** `DateField(format=None, input_formats=None)` -* `format` - A string representing the output format. If not specified, the `DATE_FORMAT` setting will be used, which defaults to `'iso-8601'`. +* `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']`. Date format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style dates should be used. (eg `'2013-01-29'`) @@ -227,7 +231,7 @@ Corresponds to `django.db.models.fields.TimeField` **Signature:** `TimeField(format=None, input_formats=None)` -* `format` - A string representing the output format. If not specified, the `TIME_FORMAT` setting will be used, which defaults to `'iso-8601'`. +* `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']`. Time format strings may either be [python strftime formats][strftime] which explicitly specifiy the format, or the special string `'iso-8601'`, which indicates that [ISO 8601][iso8601] style times should be used. (eg `'12:34:56.000000'`) @@ -273,7 +277,51 @@ Django's regular [FILE_UPLOAD_HANDLERS] are used for handling uploaded files. --- +# Custom fields + +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 intial datatype, and a primative, serializable datatype. Primative 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 primative objects. + +The `.to_native()` method is called to convert the initial datatype into a primative, serializable datatype. The `from_native()` method is called to restore a primative datatype into it's initial representation. + +## Examples + +Let's look at an example of serializing a class that represents an RGB color value: + + 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 + + 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 |