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Yii2 ManyToMany Behavior

This behavior soon will be DEPRECATED.
See the new version Yii2 Linker Behavior.

About

This behavior makes it easy to maintain many-to-many and one-to-many relations in your ActiveRecord models.

Support

GutHub issues.

Usage

1. In your model, add the behavior and configure it
2. In your model, add validation rules for the attributes created by the behavior
3. In your view, create form fields for the attributes

Adding and configuring the behavior

As an example, let's assume you are dealing with entities like Book, Author and Review. The Book model has the following relationships:

In the same model, the behaviour can be configured like so:

Relation names don't need to end in _ids, and you can use any name for a relation. It is recommended to use meaningful names, though.

Adding validation rules

The attributes are created automatically. However, you must supply a validation rule for them (usually a safe validator):

Creating form fields

By default, the behavior will accept data from a multiselect field:

Known issues and limitations

• Composite primary keys are not supported.
• Junction table for many-to-many links is updated using the connection from the primary model.
• When using a function to calculate the default value, keep in mind that this function is called once, right before the relations are saved, and then its result is used to update all relevant rows using one query.
• Relations are saved using DAO (i. e. by manipulating the tables directly).

Custom getters and setters

Attributes like author_ids and review_ids in the Book model are created automatically. By default, they are configured to accept data from a standard select input (see below). However, it is possible to use custom getter and setter functions, which may be useful for interaction with more complex frontend scripts. It is possible to define many alternative getters and setters for a given attribute:

Field name is concatenated to the attribute name with an underscore. In this example, accessing $model->author_ids will result in an array of IDs, $model->author_ids_json will return a JSON string and $model->author_ids_string will return a comma-separated string of IDs. Setters work similarly.

Getters and setters may be ommitted to fall back to default behavior (arrays of IDs).

NOTE

The setter function receives whatever data comes through the $_REQUEST and is expected to return the array of the related model IDs. The getter function receives the array of the related model IDs.

COMPATIBILITY NOTE

Specifying getters and setters for the primary attribute (author_ids in the above example) is still supported, but not recommended. Best practice is to use primary attribute to get and set values as array of IDs and create fields to use other getters and setters.

Custom junction table values

For seting additional values in junction table (apart columns required for relation), you can use viaTableValues:

Setting default values for orphaned models

When one-to-many relations are saved, old links are removed and new links are created. To remove an old link, the corresponding foreign-key column is set to a certain value. It is NULL by default, but can be configured differently. Note that your database must support your chosen default value, so if you are using NULL as a default value, the field must be nullable.

You can supply a constant value like so:

It is also possible to assign the default value to NULL explicitly, like so: 'default' => null. Another option is to provide a function to calculate the default value:

The function accepts 3 parameters. In our example $model is the instance of the Book class (owner of the behavior), $relationName is 'reviews' and $attributeName is 'review_ids'.

If you need the db connection inside this function, it is recommended to obtain it from either the primary model (Book) or the secondary model (Review).

Applying the behaviour several times to a single relationship

It is possible to use this behavior for a single relationship multiple times in a single model. This is not recommended, however.

Using the behaviour with relations that are using the same junction table

When you are implementing multiple ManyToMany relations in the same model, and they are using same junction table, you may face and issue when your junction records will not be saved properly.

This happens because old junction records are dropped each time new relation is saved. To avoid deletion of records that were just saved, you will need to set customDeleteCondition param.

This delete condition will be merged with primary delete condition and may be used to fine tune your delete query.

For example, let's imagine that we develop a scientific database for botanical laboratory. We have a model called "Sample" for different plants samples, model called "Attachment" for related files (photos or documents) and junction table "sample_attachments". And we want to divide all those files into separate fields in the "Sample" model (raw material pictures, molecular structure, etc) by introducing field "type" in the junction table. In such case, the resulting "Sample" model will look like this:

Installation

The preferred way to install this extension is through composer.

Either run

or add

to the require section of your composer.json file.