Laravel 5 Collections: Conditionally Executing a Callback On a Collection's Elements With when

The when method will execute the provided $callback on the collection if the provided boolean $value evaluates to true. A $default callback may also be supplied if the provided $value evaluates to false. Both of the provided callbacks will receive the current collection instance as their only argument; the when method has the potential to modify the original collection instance.

The when method will return a reference to the original collection instance.

#Signature

1public function when(
2    $value,
3    callable $callback,
4    callable $default = null
5);

#Example Use

The following example demonstrates the behavior of the when method. In both of the when calls we are supplying both the $callback and $default callbacks. Additionally, we are returning the collection instance within the callback functions to continue our method chain; this is because the when method will return the results of the callback.

 1$collection = collect([]);
 2
 3// The `$callback` callback will be invoked.
 4$collection->when(true, function ($collection) {
 5    $collection->push('Pushed the truth message!');
 6
 7    return $collection;
 8}, function ($collection) {
 9    $collection->push('Pushed the default message!');
10
11    return $collection;
12})
13// The `$default` callback will be invoked.
14->when(false, function ($collection) {
15    $collection->push('Pushed the truth message!');
16
17    return $collection;
18}, function ($collection) {
19    $collection->push('Pushed the default message!');
20
21    return $collection;
22});

After the above code has executed, the $collection would contain the following values:

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