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provide ValueFromContext documentation

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Max Morlocke 2020-12-23 23:22:55 -05:00
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docs/api-guide/validators.md
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@ -183,6 +183,16 @@ A default class that can be used to represent the current user. In order to use
default=serializers.CurrentUserDefault()
)
#### ValueFromContext
CurrentUserDefault is an example of extracting a value from context and setting a hidden field to this value. This pattern resurfaces in a number of contexts related to hidden fields, and you may wish to insert something other than user, such as a parent object who's ID was extracted from the URL as part of view processing. Simply pass in the value to extract from the context:
parent = serializers.HiddenField(
default=serializers.ValueFromContext("parent_object")
)
In the event that there is nested data inside the context that you need to extract, you can override ValueFromContext's call method.
#### CreateOnlyDefault
A default class that can be used to *only set a default argument during create operations*. During updates the field is omitted.