backend-relations.md

Backend Relations

• Introduction
• Configuring the relation behavior
• Relationship types
  • Has many
  • Belongs to many
  • Belongs to many (with Pivot Data)
  • Belongs to
  • Has one
• Displaying a relation manager
• Extending relation behavior
• Overriding relation partials

Introduction

The Relation behavior is a controller behavior used for easily managing complex model relationships on a page. It is not to be confused with List relation columns or Form relation fields that only provide simple management.

The Relation behavior depends on relation definitions. In order to use the relation behavior you should add the \Backend\Behaviors\RelationController::class definition to the $implement property of the controller class.

namespace Acme\Projects\Controllers;

class Projects extends Controller
{
    /**
     * @var array List of behaviors implemented by this controller
     */
    public $implement = [
        \Backend\Behaviors\FormController::class,
        \Backend\Behaviors\RelationController::class,
    ];
}

NOTE: The relation behavior is frequently used together with the form behavior.

Configuring the relation behavior

The relation behaviour will load its configuration in the YAML format from a config_relation.yaml file located in the controller's views directory (plugins/myauthor/myplugin/controllers/mycontroller/config_relation.yaml) by default.

This can be changed by overriding the $relationConfig property on your controller to reference a different filename or a full configuration array:

public $relationConfig = 'my_custom_relation_config.yaml';

The required configuration depends on the relationship type between the target model and the related model.

The first level field in the relation configuration file defines the relationship name in the target model. For example:

class Invoice {
    public $hasMany = [
        'items' => ['Acme\Pay\Models\InvoiceItem'],
    ];
}

An Invoice model with a relationship called items should define the first level field using the same relationship name:

# ===================================
#  Relation Behavior Config
# ===================================

items:
    label: Invoice Line Item
    view:
        list: $/acme/pay/models/invoiceitem/columns.yaml
        toolbarButtons: create|delete
    manage:
        form: $/acme/pay/models/invoiceitem/fields.yaml
        recordsPerPage: 10

You can also customize the labels of the toolbar buttons:

items:
    label: Invoice Line Item
    view:
        list: $/acme/pay/models/invoiceitem/columns.yaml
        toolbarButtons:
            create: Add a line item
            delete: Remove line item
    manage:
        form: $/acme/pay/models/invoiceitem/fields.yaml
        recordsPerPage: 10

The following options are then used for each relationship name definition:

<style> .attributes-table-precessor + table td:first-child, .attributes-table-precessor + table td:first-child > * { white-space: nowrap; } </style>

Option	Description
label	a label for the relation, in the singular tense, required.
view	configuration specific to the view container, see below.
manage	configuration specific to the management popup, see below.
pivot	a reference to form field definition file, used for relations with pivot table data.
emptyMessage	a message to display when the relationship is empty, optional.
readOnly	disables the ability to add, update, delete or create relations. default: false
deferredBinding	defers all binding actions using a session key when it is available. default: false

These configuration values can be specified for the view or manage options, where applicable to the render type of list, form or both.

<style> .attributes-table-precessor + table td:first-child, .attributes-table-precessor + table td:first-child > * { white-space: nowrap; } </style>

Option	Type	Description
form	Form	a reference to form field definition file, see backend form fields.
list	List	a reference to list column definition file, see backend list columns.
showSearch	List	display an input for searching the records. Default: false
showSorting	List	displays the sorting link on each column. Default: true
defaultSort	List	sets a default sorting column and direction when user preference is not defined. Supports a string or an array with keys column and direction.
recordsPerPage	List	maximum rows to display for each page.
noRecordsMessage	List	a message to display when no records are found, can refer to a localization string.
conditions	List	specifies a raw where query statement to apply to the list model query.
scope	List	specifies a query scope method defined in the related form model to apply to the list query always. The model that this relationship will be attached to (i.e. the parent model) is passed to this scope method as the second parameter ($query is the first).
filter	List	a reference to a filter scopes definition file, see backend list filters.

These configuration values can be specified only for the view options.

<style> .attributes-table-precessor + table td:first-child, .attributes-table-precessor + table td:first-child > * { white-space: nowrap; } </style>

Option	Type	Description
showCheckboxes	List	displays checkboxes next to each record.
recordUrl	List	link each list record to another page. Eg: users/update/:id. The :id part is replaced with the record identifier.
customViewPath	List	specify a custom view path to override partials used by the list.
recordOnClick	List	custom JavaScript code to execute when clicking on a record.
toolbarPartial	Both	a reference to a controller partial file with the toolbar buttons. Eg: _relation_toolbar.htm. This option overrides the toolbarButtons option.
toolbarButtons	Both	the set of buttons to display. This can be formatted as an array or a pipe separated string, or set to false to show no buttons. Available options are: create, update, delete, add, remove, link, & unlink. Example: add|remove. Additionally, you can customize the text inside these buttons by setting this property to an associative array, with the key being the button type and the value being the text for that button. Example: create: 'Assign User'. The value also supports translation.

These configuration values can be specified only for the manage options.

<style> .attributes-table-precessor + table td:first-child, .attributes-table-precessor + table td:first-child > * { white-space: nowrap; } </style>

Option	Type	Description
title	Both	a popup title, can refer to a localization string. Additionally, you can customize the title for each mode individually by setting this to an associative array, with the key being the mode and the value being the title used when displaying that mode. Eg: form: acme.blog::lang.subcategory.FormTitle.
context	Form	context of the form being displayed. Can be a string or an array with keys: create, update.

Relationship types

How the relation manager is displayed depends on the relationship definition in the target model. The relationship type will also determine the configuration requirements, these are shown in bold. The following relationship types are available:

• Has many
• Belongs to many
• Belongs to Many (with Pivot Data)
• Belongs to
• Has one

Has many

1. Related records are displayed as a list (view.list).
2. Clicking a record will display an update form (manage.form).
3. Clicking Add will display a selection list (manage.list).
4. Clicking Create will display a create form (manage.form).
5. Clicking Delete will destroy the record(s).
6. Clicking Remove will orphan the relationship.

For example, if a Blog Post has many Comments, the target model is set as the blog post and a list of comments is displayed, using columns from the list definition. Clicking on a comment opens a popup form with the fields defined in form to update the comment. Comments can be created in the same way. Below is an example of the relation behavior configuration file:

# ===================================
#  Relation Behavior Config
# ===================================

comments:
    label: Comment
    manage:
        form: $/acme/blog/models/comment/fields.yaml
        list: $/acme/blog/models/comment/columns.yaml
    view:
        list: $/acme/blog/models/comment/columns.yaml
        toolbarButtons: create|delete

Belongs to many

1. Related records are displayed as a list (view.list).
2. Clicking Add will display a selection list (manage.list).
3. Clicking Create will display a create form (manage.form).
4. Clicking Delete will destroy the pivot table record(s).
5. Clicking Remove will orphan the relationship.

For example, if a User belongs to many Roles, the target model is set as the user and a list of roles is displayed, using columns from the list definition. Existing roles can be added and removed from the user. Below is an example of the relation behavior configuration file:

# ===================================
#  Relation Behavior Config
# ===================================

roles:
    label: Role
    view:
        list: $/acme/user/models/role/columns.yaml
        toolbarButtons: add|remove
    manage:
        list: $/acme/user/models/role/columns.yaml
        form: $/acme/user/models/role/fields.yaml

Belongs to many (with Pivot Data)

1. Related records are displayed as a list (view.list).
2. Clicking a record will display an update form (pivot.form).
3. Clicking Add will display a selection list (manage.list), then a data entry form (pivot.form).
4. Clicking Remove will destroy the pivot table record(s).

Continuing the example in Belongs To Many relations, if a role also carried an expiry date, clicking on a role will open a popup form with the fields defined in pivot to update the expiry date. Below is an example of the relation behavior configuration file:

# ===================================
#  Relation Behavior Config
# ===================================

roles:
    label: Role
    view:
        list: $/acme/user/models/role/columns.yaml
    manage:
        list: $/acme/user/models/role/columns.yaml
    pivot:
        form: $/acme/user/models/role/fields.yaml

Pivot data is available when defining form fields and list columns via the pivot relation, see the example below:

# ===================================
#  Relation Behavior Config
# ===================================

teams:
    label: Team
    view:
        list:
            columns:
                name:
                    label: Name
                pivot[team_color]:
                    label: Team color
    manage:
        list:
            columns:
                name:
                    label: Name
    pivot:
        form:
            fields:
                pivot[team_color]:
                    label: Team color

Belongs to

1. Related record is displayed as a preview form (view.form).
2. Clicking Create will display a create form (manage.form).
3. Clicking Update will display an update form (manage.form).
4. Clicking Link will display a selection list (manage.list).
5. Clicking Unlink will orphan the relationship.
6. Clicking Delete will destroy the record.

For example, if a Phone belongs to a Person the relation manager will display a form with the fields defined in form. Clicking the Link button will display a list of People to associate with the Phone. Clicking the Unlink button will dissociate the Phone with the Person.

# ===================================
#  Relation Behavior Config
# ===================================

person:
    label: Person
    view:
        form: $/acme/user/models/person/fields.yaml
        toolbarButtons: link|unlink
    manage:
        form: $/acme/user/models/person/fields.yaml
        list: $/acme/user/models/person/columns.yaml

Has one

1. Related record is displayed as a preview form (view.form).
2. Clicking Create will display a create form (manage.form).
3. Clicking Update will display an update form (manage.form).
4. Clicking Link will display a selection list (manage.list).
5. Clicking Unlink will orphan the relationship.
6. Clicking Delete will destroy the record.

For example, if a Person has one Phone the relation manager will display form with the fields defined in form for the Phone. When clicking the Update button, a popup is displayed with the fields now editable. If the Person already has a Phone the fields are update, otherwise a new Phone is created for them.

# ===================================
#  Relation Behavior Config
# ===================================

phone:
    label: Phone
    view:
        form: $/acme/user/models/phone/fields.yaml
        toolbarButtons: update|delete
    manage:
        form: $/acme/user/models/phone/fields.yaml
        list: $/acme/user/models/phone/columns.yaml

Displaying a relation manager

Before relations can be managed on any page, the target model must first be initialized in the controller by calling the initRelation method.

$post = Post::where('id', 7)->first();
$this->initRelation($post);

NOTE: The form behavior will automatically initialize the model on its create, update and preview actions.

The relation manager can then be displayed for a specified relation definition by calling the relationRender method. For example, if you want to display the relation manager on the Preview page, the preview.htm view contents could look like this:

<?= $this->formRenderPreview() ?>

<?= $this->relationRender('comments') ?>

You may instruct the relation manager to render in read only mode by passing the option as the second argument:

<?= $this->relationRender('comments', ['readOnly' => true]) ?>

Extending relation behavior

Sometimes you may wish to modify the default relation behavior and there are several ways you can do this.

• Extending relation configuration
• Extending the view widget
• Extending the manage widget
• Extending the pivot widget
• Extending the filter widgets
• Extending refresh results

Extending relation configuration

Provides an opportunity to manipulate the relation configuration. The following example can be used to inject a different columns.yaml file based on a property of your model.

public function relationExtendConfig($config, $field, $model)
{
    // Make sure the model and field matches those you want to manipulate
    if (!$model instanceof MyModel || $field != 'myField')
        return;

    // Show a different list for business customers
    if ($model->mode == 'b2b') {
        $config->view['list'] = '$/author/plugin_name/models/mymodel/b2b_columns.yaml';
    }
}

Extending the view widget

Provides an opportunity to manipulate the view widget.

NOTE: The view widget has not yet fully initialized, so not all public methods will work as expected! For more information read How to remove a column.

For example you might want to toggle showCheckboxes based on a property of your model.

public function relationExtendViewWidget($widget, $field, $model)
{
    // Make sure the model and field matches those you want to manipulate
    if (!$model instanceof MyModel || $field != 'myField')
        return;

    if ($model->constant) {
        $widget->showCheckboxes = false;
    }
}

How to remove a column

Since the widget has not completed initializing at this point of the runtime cycle you can't call $widget->removeColumn(). The addColumns() method as described in the ListController documentation will work as expected, but to remove a column we need to listen to the 'list.extendColumns' event within the relationExtendViewWidget() method. The following example shows how to remove a column:

public function relationExtendViewWidget($widget, $field, $model)
{
    // Make sure the model and field matches those you want to manipulate
    if (!$model instanceof MyModel || $field != 'myField')
        return;

    // Will not work!
    $widget->removeColumn('my_column');

    // This will work
    $widget->bindEvent('list.extendColumns', function () use($widget) {
        $widget->removeColumn('my_column');
    });
}

Extending the manage widget

Provides an opportunity to manipulate the manage widget of your relation.

public function relationExtendManageWidget($widget, $field, $model)
{
    // Make sure the field is the expected one
    if ($field != 'myField')
        return;

    // manipulate widget as needed
}

Extending the pivot widget

Provides an opportunity to manipulate the pivot widget of your relation.

public function relationExtendPivotWidget($widget, $field, $model)
{
    // Make sure the field is the expected one
    if ($field != 'myField')
        return;

    // manipulate widget as needed
}

Extending the filter widgets

There are two filter widgets that may be extended using the following methods, one for the view mode and one for the manage mode of the RelationController.

public function relationExtendViewFilterWidget($widget, $field, $model)
{
    // Extends the view filter widget
}

public function relationExtendManageFilterWidget($widget, $field, $model)
{
    // Extends the manage filter widget
}

Examples on how to add or remove scopes programmatically in the filter widgets can be found in the Extending filter scopes section of the backend list documentation.

Extending the refresh results

The view widget is often refreshed when the manage widget makes a change, you can use this method to inject additional containers when this process occurs. Return an array with the extra values to send to the browser, eg:

public function relationExtendRefreshResults($field)
{
    // Make sure the field is the expected one
    if ($field != 'myField')
        return;

    return ['#myCounter' => 'Total records: 6'];
}

Overriding relation partials

Sometimes you may wish to override the default relation partials. To do so, create a file with the same name as the default partial, but prepend it with _relation and store it within your controllers directory. Your partial will be autodetected and used instead of the default one.

Let's say you want to override the _manage_form.htm partial. Create a file within your controllers directory, and name it _relation_manage_form.htm.