[5.5] groupBy method in collection to support multiple levels

[patriziotomato]

Ever wanted to groupBy multiple levels? Simply specify the groupBy-criteria(s) as an array. Each array element will applied for the particular level within a multidimensional tree structure. For each level, the groupBy method works exactly the way before, so you can still use a callback for any level for example.

No clue what I'm talking about? Then take a look at the corresponding test helps maybe:

public function testGroupByMultiLevelAndClosurePreservingKeys()
{
    $data = new Collection([
        10 => ['user' => 1, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_3']],
        20 => ['user' => 2, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_2']],
        30 => ['user' => 3, 'skilllevel' => 2, 'roles' => ['Role_1']],
        40 => ['user' => 4, 'skilllevel' => 2, 'roles' => ['Role_2']],
    ]);

    $result = $data->groupBy([
        'skilllevel',
        function ($item) {
            return $item['roles'];
        },
    ], true);

    $expected_result = [
        1 => [
            'Role_1' => [
                10 => ['user' => 1, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_3']],
                20 => ['user' => 2, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_2']],
            ],
            'Role_3' => [
                10 => ['user' => 1, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_3']],
            ],
            'Role_2' => [
                20 => ['user' => 2, 'skilllevel' => 1, 'roles' => ['Role_1', 'Role_2']],
            ],
        ],
        2 => [
            'Role_1' => [
                30 => ['user' => 3, 'skilllevel' => 2, 'roles' => ['Role_1']],
            ],
            'Role_2' => [
                40 => ['user' => 4, 'skilllevel' => 2, 'roles' => ['Role_2']],
            ],
        ],
    ];

    $this->assertEquals($expected_result, $result->toArray());
}

Even cooler if you can combine that with dot-syntax of array_get():

$user40 = array_get($result, '2.Role_2')->first();

[decadence]

@patriziotomato can you explain how works

function ($item) {
    return $item['roles'];
},

if it returns array and not simple value for grouping?

[patriziotomato]

@decadence Sorry, don't get your question. $items['roles'] returns an array of roles if you refer to the test testGroupByMultiLevelAndClosurePreservingKeys

[decadence]

Yes. It returns array but doesn't groupBy callback criteria need to return value that can be array key for group? Array can't be array key AFAIK.

[patriziotomato]

More precisely a callback function (returning an array) will be passed to groupBy-function. In this case the method behave exactly as it was before my change.

The method then take the array items of the callback function as keys to group by.

This is the relevant part where this magic is happing.

// Here, the group keys of the callback function are used instead of a concrete value.
$groupKeys = $groupBy($value, $key);

if (! is_array($groupKeys)) {
    $groupKeys = [$groupKeys];
}

foreach ($groupKeys as $groupKey) {
	// grouping logic
}

You are right, that passing an array won't work, but in this case the callback is doing the magic. Hope this helps to clarify this.

[decadence]

@patriziotomato thanks for explanation. I didn't know that callback can return array of keys and item will be added to each group for these keys.

[patriziotomato]

@decadence Me too ;) Looks like the example in the test is a good one...