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divide docs in sections, provide Meta attributes inheritance, add tests for fastapi use wih mixins and concrete

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collerek
2020-12-11 15:51:29 +01:00
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docs/models/inheritance.md Normal file
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# Inheritance
Out of various types of ORM models inheritance `ormar` currently supports two of them:
* **Mixins**
* **Concrete table inheritance** (with parents set to `abstract=True`)
## Types of inheritance
The short summary of different types of inheritance is:
* **Mixins [SUPPORTED]** - don't even subclass `ormar.Model`, just define fields that are later used on several different models (like `created_date` and `updated_date` on each model), only actual models create tables but those fields from mixins are added
* **Concrete table inheritance [SUPPORTED]** - means that parent is marked as abstract and each child has it's own table with columns from parent and own child columns, kind of similar to Mixins but parent also is a Model
* **Single table inheritance [NOT SUPPORTED]** - means that only one table is created with fields that are combination/sum of the parent and all children models but child models use only subset of column in db (all parent and own ones, skipping the other children ones)
* **Multi/ Joined table inheritance [NOT SUPPORTED]** - means that part of the columns is saved on parent model and part is saved on child model that are connected to each other by kind of one to one relation and under the hood you operate on two models at once
* **Proxy models [NOT SUPPORTED]** - means that only parent has an actual table, children just add methods, modify settings etc.
## Mixins
To use Mixins just define a class that is not inheriting from an `ormar.Model` but is defining `ormar.Fields` as class variables.
```python
# a mixin defines the fields but is a normal python class
class AuditMixin:
created_by: str = ormar.String(max_length=100)
updated_by: str = ormar.String(max_length=100, default="Sam")
class DateFieldsMixins:
created_date: datetime.datetime = ormar.DateTime(default=datetime.datetime.now)
updated_date: datetime.datetime = ormar.DateTime(default=datetime.datetime.now)
# a models can inherit from one or more mixins
class Category(ormar.Model, DateFieldsMixins, AuditMixin):
class Meta(ormar.ModelMeta):
tablename = "categories"
metadata = metadata
database = db
id: int = ormar.Integer(primary_key=True)
name: str = ormar.String(max_length=50, unique=True, index=True)
code: int = ormar.Integer()
```
!!!note
Note that Mixins are **not** models, so you still need to inherit from `ormar.Model` as well as define `Meta` class in the final model.
A Category class above will have four additional fields: `created_date`, `updated_date`, `created_by` and `updated_by`.
There will be only one table created for model Category, with `Category` class fields combined with all `Mixins` fields.
Note that Mixin in class name is optional but is a good python practice.
!!!warning
You cannot declare a field in a `Model` that is already defined in one of the `Mixins` you inherit from.
So in example above `Category` cannot declare it's own `created_date` as this filed will be inherited from `DateFieldsMixins`.
If you try to the `ModelDefinitionError` will be raised.
## Concrete table inheritance
In concept concrete table inheritance is very similar to Mixins, but uses actual `ormar.Models` as base classes.
!!!warning
Note that base classes have `abstract=True` set in `Meta` class, if you try to inherit from non abstract marked class `ModelDefinitionError` will be raised.
Since this abstract Model will never be initialized you can skip `metadata` and `database` in it's `Meta` definition.
But if you provide it - it will be inherited, that way you do not have to provide `metadata` and `databases` in concrete class
Note that you can always overwrite it in child/concrete class if you need to.
More over at least one of the classes in inheritance chain have to provide it - otherwise an error will be raised.
```python
# note that base classes have abstract=True
# since this model will never be initialized you can skip metadata and database
class AuditModel(ormar.Model):
class Meta:
abstract = True
created_by: str = ormar.String(max_length=100)
updated_by: str = ormar.String(max_length=100, default="Sam")
# but if you provide it it will be inherited
class DateFieldsModel(ormar.Model):
class Meta:
abstract = True
metadata = metadata
database = db
created_date: datetime.datetime = ormar.DateTime(default=datetime.datetime.now)
updated_date: datetime.datetime = ormar.DateTime(default=datetime.datetime.now)
# that way you do not have to provide metadata and databases in concrete class
class Category(DateFieldsModel, AuditModel):
class Meta(ormar.ModelMeta):
tablename = "categories"
id: int = ormar.Integer(primary_key=True)
name: str = ormar.String(max_length=50, unique=True, index=True)
code: int = ormar.Integer()
```
The list of inherited options/settings is as follows: `metadata`, `database` and `constraints`.
Also methods decorated with `@property_field` decorator will be inherited/recognized.
Of course apart from that all fields from base classes are combined and created in the concrete table of the final Model.
!!!warning
You cannot declare a field in a `Model` that is already defined in one of the `Mixins` you inherit from.
So in example above `Category` cannot declare it's own `created_date` as this filed will be inherited from `DateFieldsMixins`.
If you try to the `ModelDefinitionError` will be raised.

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@ -45,11 +45,43 @@ class Department(ormar.Model):
!!!tip
Reverse ForeignKey allows you to query the related models with [queryset-proxy][queryset-proxy].
It allows you to use `await department.courses.all()` to fetch data related only to specific department etc.
##ManyToMany
To define many-to-many relation use `ManyToMany` field.
```python hl_lines="25-26"
class Category(ormar.Model):
class Meta:
tablename = "categories"
database = database
metadata = metadata
id: int = ormar.Integer(primary_key=True)
name: str = ormar.String(max_length=40)
# note: you need to specify through model
class PostCategory(ormar.Model):
class Meta:
tablename = "posts_categories"
database = database
metadata = metadata
class Post(ormar.Model):
class Meta:
tablename = "posts"
database = database
metadata = metadata
id: int = ormar.Integer(primary_key=True)
title: str = ormar.String(max_length=200)
categories: Optional[Union[Category, List[Category]]] = ormar.ManyToMany(
Category, through=PostCategory
)
```
!!!tip
To read more about many-to-many relations visit [many-to-many][many-to-many] section
@ -58,6 +90,8 @@ To define many-to-many relation use `ManyToMany` field.
!!!tip
ManyToMany allows you to query the related models with [queryset-proxy][queryset-proxy].
It allows you to use `await post.categories.all()` but also `await category.posts.all()` to fetch data related only to specific post, category etc.
[foreign-keys]: ./foreign-key.md
[many-to-many]: ./many-to-many.md

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# 0.7.3
* Fix for setting fetching related model with UUDI pk, which is a string in raw (fix [#71][#71])
# 0.7.2
* Fix for overwriting related models with pk only in `Model.update() with fields passed as parameters` (fix [#70][#70])
@ -188,4 +192,5 @@ Add queryset level methods
[#19]: https://github.com/collerek/ormar/issues/19
[#60]: https://github.com/collerek/ormar/issues/60
[#68]: https://github.com/collerek/ormar/issues/68
[#70]: https://github.com/collerek/ormar/issues/70
[#70]: https://github.com/collerek/ormar/issues/70
[#71]: https://github.com/collerek/ormar/issues/71