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many to many docs

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Tobe O 2019-04-02 19:12:35 -04:00
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@ -175,19 +175,11 @@ Relationships use joins when possible, but in the case of `@HasMany()`, two quer
## Many to Many Relations
A many-to-many relationship can now be modeled like so.
`UserRole` in this case is a pivot table joining `User` and `Role`.
`RoleUser` in this case is a pivot table joining `User` and `Role`.
Note that in this case, the models must reference the private classes (`_User`, etc.), because the canonical versions (`User`, etc.) are not-yet-generated:
```dart
library angel_orm_generator.test.models.user;
import 'package:angel_model/angel_model.dart';
import 'package:angel_orm/angel_orm.dart';
import 'package:angel_serialize/angel_serialize.dart';
import 'package:collection/collection.dart';
part 'user.g.dart';
@serializable
@orm
abstract class _User extends Model {
@ -195,10 +187,18 @@ abstract class _User extends Model {
String get password;
String get email;
@hasMany
List<_UserRole> get userRoles;
@ManyToMany(_RoleUser)
List<_Role> get roles;
}
List<_Role> get roles => userRoles.map((m) => m.role).toList();
@serializable
@orm
abstract class _RoleUser {
@belongsTo
_Role get role;
@belongsTo
_User get user;
}
@serializable
@ -206,35 +206,19 @@ abstract class _User extends Model {
abstract class _Role extends Model {
String name;
@hasMany
List<_UserRole> get userRoles;
List<_User> get users => userRoles.map((m) => m.user).toList();
}
@Serializable(autoIdAndDateFields: false)
@orm
abstract class _UserRole {
int get id;
@belongsTo
_User get user;
@belongsTo
_Role get role;
@ManyToMany(_RoleUser)
List<_User> get users;
}
```
TLDR:
1. Make a pivot table, C, between two tables, table A and B
2. C should `@belongsTo` both A and B.
3. Both A and B should `@hasMany` C.
4. For convenience, write a simple getter, like the above `User.roles`.
2. C should `@belongsTo` both A and B. C *should not* extend `Model`.
3. A should have a field: `@ManyToMany(_C) List<_B> get b;`
4. B should have a field: `@ManyToMany(_C) List<_A> get a;`
Test: https://raw.githubusercontent.com/angel-dart/orm/master/angel_orm_generator/test/many_to_many_test.dart
There are 2 tests there, but they are more or less a proof-of-concept. All the logic for the other relations have their own unit tests.
# Columns
Use a `@Column()` annotation to change how a given field is handled within the ORM.