Mixin Mixin
View code Creating assocations in sequelize is done by calling one of the belongsTo / hasOne / hasMany functions on a model (the source), and prodiving another model as the first argument to the function (the target).
- hasOne - adds a foreign key to target
- belongsTo - add a foreign key to source
- hasMany - adds a foreign key to target, unless you also specifiy that target hasMany source, in which case a junction table is created with sourceId and targetId
Creating an association will add a foreign key constraint to the attributes. All associations use CASCADE on update and SET NULL on delete, except for n:m, which also uses CASCADE on delete.
When creating associations, you can provide an alias, via the as option. This is usefull if the same model
is associated twice, or you want your association to be called something other than the name of the target model.
As an example, consider the case where users have many pictures, one of which is their profile picture. All pictures
have a userId, but in addition the user model also has a profilePictureId, to be able to easily load the user's profile
picture.
User.hasMany(Picture)
User.belongsTo(Picture, { as: 'ProfilePicture', constraints: false })
user.getPictures() // gets you all pictures
user.getProfilePicture() // gets you only the profile picture
User.findAll({
where: ...,
include: [
{ model: Picture }, // load all pictures
{ model: Picture, as: 'ProfilePicture' }, // load the profile picture. Notice that the spelling must be the exact same as the one in the association
]
})
To get full control over the foreign key column added by sequelize, you can use the foreignKey option. It can either be a string, that specifies the name, or and object type definition,
equivalent to those passed to sequelize.define.
User.hasMany(Picture, { foreignKey: 'uid' })
The foreign key column in Picture will now be called uid instead of the default userId.
User.hasMany(Picture, {
foreignKey: {
name: 'uid'
allowNull: false
}
})
This specifies that the uid column can not be null. In most cases this will already be covered by the foreign key costraints, which sequelize creates automatically,
but can be usefull in case where the foreign keys are disabled, e.g. due to circular references (see constraints: false below).
When fetching associated models, you can limit your query to only load some models. These queries are written in the same way as queries to find/findAll. To only get pictures in JPG, you can do:
user.getPictures({
where: {
format: 'jpg'
}
})
There are several ways to update and add new assoications. Continuing with our example of users and pictures:
user.addPicture(p) // Add a single picture
user.setPictures([p1, p2]) // Associate user with ONLY these two picture, all other associations will be deleted
user.addPictures([p1, p2]) // Associate user with these two pictures, but don't touch any current associations
You don't have to pass in a complete object to the association functions, if your associated model has a single primary key:
user.addPicture(req.query.pid) // Here pid is just an integer, representing the primary key of the picture
In the example above we have specified that a user belongs to his profile picture. Conceptually, this might not make sense,
but since we want to add the foreign key to the user model this is the way to do it.
Note how we also specified constraints: false for profile picture. This is because we add a foreign key from
user to picture (profilePictureId), and from picture to user (userId). If we were to add foreign keys to both, it would
create a cyclic dependency, and sequelize would not know which table to create first, since user depends on picture, and picture
depends on user. These kinds of problems are detected by sequelize before the models are synced to the database, and you will
get an error along the lines of Error: Cyclic dependency found. 'users' is dependent of itself. If you encounter this,
you should either disable some constraints, or rethink your associations completely.
hasOne(target, [options])
View code Creates an association between this (the source) and the provided target. The foreign key is added on the target.
Example: User.hasOne(Profile). This will add userId to the profile table.
The following methods are injected on the source:
- get[AS] - for example getProfile(finder). The finder object is passed to
target.find. - set[AS] - for example setProfile(instance, options). Options are passed to
target.save - create[AS] - for example createProfile(value, options). Builds and saves a new instance of the associated model. Values and options are passed on to
target.create
All methods return a promise
Params:
| Name | Type | Description |
|---|---|---|
| target | Model | |
| [options] | object | |
| [options.hooks=false] | boolean | Set to true to run before-/afterDestroy hooks when an associated model is deleted because of a cascade. For example if User.hasOne(Profile, {onDelete: 'cascade', hooks:true}), the before-/afterDestroy hooks for profile will be called when a user is deleted. Otherwise the profile will be deleted without invoking any hooks |
| [options.as] | string | The alias of this model, in singular form. See also the name option passed to sequelize.define. If you create multiple associations between the same tables, you should provide an alias to be able to distinguish between them. If you provide an alias when creating the assocition, you should provide the same alias when eager loading and when getting assocated models. Defaults to the singularized name of target |
| [options.foreignKey] | string | object | The name of the foreign key in the target table or an object representing the type definition for the foreign column (see Sequelize.define for syntax). When using an object, you can add a name property to set the name of the colum. Defaults to the name of source + primary key of source |
| [options.onDelete='SET NULL'] | string | |
| [options.onUpdate='CASCADE'] | string | |
| [options.constraints=true] | boolean | Should on update and on delete constraints be enabled on the foreign key. |
belongsTo(target, [options])
View code Creates an association between this (the source) and the provided target. The foreign key is added on the source.
Example: Profile.belongsTo(User). This will add userId to the profile table.
The following methods are injected on the source:
- get[AS] - for example getUser(finder). The finder object is passed to
target.find. - set[AS] - for example setUser(instance, options). Options are passed to this.save
- create[AS] - for example createUser(value, options). Builds and saves a new instance of the associated model. Values and options are passed on to target.create
All methods return a promise
Params:
| Name | Type | Description |
|---|---|---|
| target | Model | |
| [options] | object | |
| [options.hooks=false] | boolean | Set to true to run before-/afterDestroy hooks when an associated model is deleted because of a cascade. For example if User.hasOne(Profile, {onDelete: 'cascade', hooks:true}), the before-/afterDestroy hooks for profile will be called when a user is deleted. Otherwise the profile will be deleted without invoking any hooks |
| [options.as] | string | The alias of this model, in singular form. See also the name option passed to sequelize.define. If you create multiple associations between the same tables, you should provide an alias to be able to distinguish between them. If you provide an alias when creating the assocition, you should provide the same alias when eager loading and when getting assocated models. Defaults to the singularized name of target |
| [options.foreignKey] | string | object | The name of the foreign key in the source table or an object representing the type definition for the foreign column (see Sequelize.define for syntax). When using an object, you can add a name property to set the name of the colum. Defaults to the name of target + primary key of target |
| [options.onDelete='SET NULL'] | string | |
| [options.onUpdate='CASCADE'] | string | |
| [options.constraints=true] | boolean | Should on update and on delete constraints be enabled on the foreign key. |
hasMany(target, [options])
View code Create an association that is either 1:m or n:m.
// Create a 1:m association between user and project
User.hasMany(Project)
// Create a n:m association between user and project
User.hasMany(Project)
Project.hasMany(User)
By default, the name of the join table will be source+target, so in this case projectsusers. This can be overridden by providing either a string or a Model as through in the options.
The following methods are injected on the source:
- get[AS] - for example getPictures(finder). The finder object is passed to
target.find. - set[AS] - for example setPictures(instances, defaultAttributes|options). Update the associations. All currently associated models that are not in instances will be removed.
- add[AS] - for example addPicture(instance, defaultAttributes|options). Add another associated object.
- add[AS] [plural] - for example addPictures([instance1, instance2], defaultAttributes|options). Add some more associated objects.
- create[AS] - for example createPicture(values, options). Build and save a new association.
- remove[AS] - for example removePicture(instance). Remove a single association.
- remove[AS] [plural] - for example removePictures(instance). Remove multiple association.
- has[AS] - for example hasPicture(instance). Is source associated to this target?
- has[AS] [plural] - for example hasPictures(instances). Is source associated to all these targets?
All methods return a promise
If you use a through model with custom attributes, these attributes can be set when adding / setting new associations in two ways. Consider users and projects from before with a join table that stores whether the project has been started yet:
var UserProjects = sequelize.define('userprojects', {
started: Sequelize.BOOLEAN
})
User.hasMany(Project, { through: UserProjects })
Project.hasMany(User, { through: UserProjects })
jan.addProject(homework, { started: false }) // The homework project is not started yet
jan.setProjects([makedinner, doshopping], { started: true}) // Both shopping and dinner has been started
If you want to set several target instances, but with different attributes you have to set the attributes on the instance, using a property with the name of the through model:
p1.userprojects {
started: true
}
user.setProjects([p1, p2], {started: false}) // The default value is false, but p1 overrides that.
Similarily, when fetching through a join table with custom attributes, these attributes will be available as an object with the name of the through model.
user.getProjects().success(function (projects) {
var p1 = projects[0]
p1.userprojects.started // Is this project started yet?
})
Params:
| Name | Type | Description |
|---|---|---|
| target | Model | |
| [options] | object | |
| [options.hooks=false] | boolean | Set to true to run before-/afterDestroy hooks when an associated model is deleted because of a cascade. For example if User.hasOne(Profile, {onDelete: 'cascade', hooks:true}), the before-/afterDestroy hooks for profile will be called when a user is deleted. Otherwise the profile will be deleted without invoking any hooks |
| [options.through] | Model | string | object |
| [options.through.model] | Model | The model used to join both sides of the N:M association. |
| [options.through.scope] | object | A key/value set that will be used for association create and find defaults on the through model. (Remember to add the attributes to the through model) |
| [options.through.unique=true] | boolean | If true a unique key will be generated from the foreign keys used (might want to turn this off and create specific unique keys when using scopes) |
| [options.as] | string | object | The alias of this model. If you provide a string, it should be plural, and will be singularized using node.inflection. If you want to control the singular version yourself, provide an object with plural and singular keys. See also the name option passed to sequelize.define. If you create multiple associations between the same tables, you should provide an alias to be able to distinguish between them. If you provide an alias when creating the assocition, you should provide the same alias when eager loading and when getting assocated models. Defaults to the pluralized name of target |
| [options.foreignKey] | string | object | The name of the foreign key in the target table / join table or an object representing the type definition for the foreign column (see Sequelize.define for syntax). When using an object, you can add a name property to set the name of the colum. Defaults to the name of source + primary key of source |
| [options.scope] | object | A key/value set that will be used for association create and find defaults on the target. (sqlite not supported for N:M) |
| [options.onDelete='SET NULL | CASCADE'] | string |
| [options.onUpdate='CASCADE'] | string | |
| [options.constraints=true] | boolean | Should on update and on delete constraints be enabled on the foreign key. |
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