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Fetch Operation PRO

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About

This operation allows an EntityCrudController to respond to AJAX requests with entries in the database for a different entity, in a format that can be used by the relationship, select2_from_ajax and select2_from_ajax_multiple fields.

Requirements

This is a PRO operation. It requires that you have purchased access to backpack/pro.

How to Use

In order to enable this operation, in your CrudController you need to use the FetchOperation trait and add a new method that responds to the AJAX requests (following the naming convention fetchEntityName()). For example, for a Tag model you'd do:

    use \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation;

    protected function fetchTag()
    {
        return $this->fetch(\App\Models\Tag::class);
    }

To customize the FetchOperation, pass an array to the fetch() call, rather than a class name. For example:

<?php

namespace App\Http\Controllers\Admin;

use Backpack\CRUD\app\Http\Controllers\CrudController;

class ProductCrudController extends CrudController
{
    use \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation;

    protected function fetchTag()
    {
        return $this->fetch([
            'model' => \App\Models\Tag::class, // required
            'searchable_attributes' => ['name', 'description'],
            'paginate' => 10, // items to show per page
            'searchOperator' => 'LIKE',
            'query' => function($model) {
                return $model->active();
            } // to filter the results that are returned
        ]);
    }
}

You can now point your AJAX select to this route, which will be backpack_url('your-main-entity/fetch/tag') .

How It Works

Based on the fact that the fetchTag() method exists, the Fetch operation will create a /product/fetch/tag POST route, which points to fetchTag(). Inside fetchTag() we call fetch(), that responds with entries in the format select2 needs.

Preventing FetchOperation from guessing the searchable attributes

If not specified searchable_attributes will be automatically inferred from model database columns. To prevent this behaviour you can setup an empty searchable_attributes array. For example:

public function fetchUser() {
        return $this->fetch([
            'model' => User::class,
            'query' => function($model) {
                $search = request()->input('q') ?? false;
                if ($search) {
                    return $model->whereRaw('CONCAT(`first_name`," ",`last_name`) LIKE "%' . $search . '%"');
                }else{
                    return $model;
                }
            },
            'searchable_attributes' => []
        ]);
    }

Using FetchOperation with select2_ajax filter

The FetchOperation can also be used as the source URL for the select2_ajax filter. To do that, we need to:

• change the select2_ajax filter method from GET (its default) to POST (what FetchOperation uses);
• tell the filter what attribute we want to show to the user;

$this->crud->addFilter([
  'name'        => 'category_id',
  'type'        => 'select2_ajax',
  'label'       => 'Category',
  'placeholder' => 'Pick a category',
  'method' => 'POST', // mandatory change
  // 'select_attribute' => 'name' // the attribute that will be shown to the user by default 'name'
  // 'select_key' => 'id' // by default is ID, change it if your model uses some other key
],
backpack_url('product/fetch/category'), // the fetch route on the ProductCrudController 
function($value) { // if the filter is active
    // $this->crud->addClause('where', 'category_id', $value);
});

How to Overwrite

In case you need to change how this operation works, it's best to take a look at the FetchOperation.php trait to understand how it works. It's a pretty simple operation. Most common ways to overwrite the Fetch operation are documented below:

Change the fetch database search operator

You can customize the search operator for FetchOperation just like you can in ListOperation. By default it's LIKE, but you can:

• change the operator individually for each fetchEntity using searchOperator => 'ILIKE' in the fetch configuration;
• change the operator for all FetchOperations inside that CrudPanel by doing:

  public function setupFetchOperationOperation() {
      $this->crud->setOperationSetting('searchOperator', 'ILIKE');
  }

• change the operator globally in your project, by creating a config file in config/backpack/operations/fetch.php and add the following:

  <?php
  return [
  'searchOperator' => 'ILIKE',
  ];

Custom behaviour for one fetch method

To make a fetchCategory() method behave differently, you can copy-paste the logic inside the FetchOperation::fetch() and change it to do whatever you need. Instead of returning $this->fetch() you can return your own results, in this case fetch will only setup the ajax route for you.

Custom behaviour for multiple fetch methods inside a Controller

To make all calls to fetch() inside an EntityCrudController behave differently, you can easily overwrite the fetch() method in that controller:

use \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation;

public function fetch($arg)
{
    // your custom code here
}

Then all $this->fetch() calls from that Controller will be using your custom code.

In case you need to call the original fetch() method (from the trait) inside your custom fetch() method (inside the controller), you can do:

use \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation { fetch as traitFetch; }

public function fetch($arg)
{
    // your custom code here

    // call the method in the trait
    return $this->traitFetch();
}

Custom behaviour for all fetch calls, in all Controllers

If you want all your fetch() calls to behave differently, no matter what Controller they are in, you can:

• duplicate the FetchOperation trait inside your application;
• instead of using \Backpack\CRUD\app\Http\Controllers\Operations\FetchOperation inside your controllers, use your custom operation trait;