diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ref/models/instances.txt | 37 | ||||
| -rw-r--r-- | docs/releases/1.10.txt | 6 |
2 files changed, 30 insertions, 13 deletions
diff --git a/docs/ref/models/instances.txt b/docs/ref/models/instances.txt index f1fc3e60e6..e63db64ae0 100644 --- a/docs/ref/models/instances.txt +++ b/docs/ref/models/instances.txt @@ -73,13 +73,12 @@ when loading from the database. The ``db`` argument contains the database alias for the database the model is loaded from, ``field_names`` contains the names of all loaded fields, and ``values`` contains the loaded values for each field in ``field_names``. The -``field_names`` are in the same order as the ``values``, so it is possible to -use ``cls(**(zip(field_names, values)))`` to instantiate the object. If all -of the model's fields are present, then ``values`` are guaranteed to be in -the order ``__init__()`` expects them. That is, the instance can be created -by ``cls(*values)``. It is possible to check if all fields are present by -consulting ``cls._deferred`` - if ``False``, then all fields have been loaded -from the database. +``field_names`` are in the same order as the ``values``. If all of the model's +fields are present, then ``values`` are guaranteed to be in the order +``__init__()`` expects them. That is, the instance can be created by +``cls(*values)``. If any fields are deferred, they won't appear in +``field_names``. In that case, assign a value of ``django.db.models.DEFERRED`` +to each of the missing fields. In addition to creating the new model, the ``from_db()`` method must set the ``adding`` and ``db`` flags in the new instance's ``_state`` attribute. @@ -87,14 +86,20 @@ In addition to creating the new model, the ``from_db()`` method must set the Below is an example showing how to record the initial values of fields that are loaded from the database:: + from django.db.models import DEFERRED + @classmethod def from_db(cls, db, field_names, values): - # default implementation of from_db() (could be replaced - # with super()) - if cls._deferred: - instance = cls(**zip(field_names, values)) - else: - instance = cls(*values) + # Default implementation of from_db() (subject to change and could + # be replaced with super()). + if len(values) != len(cls._meta.concrete_fields): + values = list(values) + values.reverse() + values = [ + values.pop() if f.attname in field_names else DEFERRED + for f in cls._meta.concrete_fields + ] + new = cls(*values) instance._state.adding = False instance._state.db = db # customization to store the original field values on the instance @@ -114,6 +119,12 @@ The example above shows a full ``from_db()`` implementation to clarify how that is done. In this case it would of course be possible to just use ``super()`` call in the ``from_db()`` method. +.. versionchanged:: 1.10 + + In older versions, you could check if all fields were loaded by consulting + ``cls._deferred``. This attribute is removed and + ``django.db.models.DEFERRED`` is new. + Refreshing objects from database ================================ diff --git a/docs/releases/1.10.txt b/docs/releases/1.10.txt index f688758a91..8de01e4fc7 100644 --- a/docs/releases/1.10.txt +++ b/docs/releases/1.10.txt @@ -783,6 +783,12 @@ Miscellaneous Web servers already implement this behavior. Responses retrieved using the Django test client continue to have these "response fixes" applied. +* ``Model.__init__()`` now receives ``django.db.models.DEFERRED`` as the value + of deferred fields. + +* The ``Model._deferred`` attribute is removed as dynamic model classes when + using ``QuerySet.defer()`` and ``only()`` is removed. + .. _deprecated-features-1.10: Features deprecated in 1.10 |