Laravel Collections Using reduce()
Example
The reduce method reduces the collection to a single value, passing the result of each iteration into the subsequent iteration. Please see reduce method.
The reduce method loops through each item with a collection and produces new result to the next iteration. Each result from the last iteration is passed through the first parameter (in the following examples, as $carry).
This method can do a lot of processing on large data sets. For example the following examples, we will use the following example student data:
$student = [
['class' => 'Math', 'score' => 60],
['class' => 'English', 'score' => 61],
['class' => 'Chemistry', 'score' => 50],
['class' => 'Physics', 'score' => 49],
];
Sum student's total score
$sum = collect($student)
->reduce(function($carry, $item){
return $carry + $item["score"];
}, 0);
Result: 220
Explanation:
$carryis the result from the last iteration.- The second parameter is the default value for the $carry in the first round of iteration. This case, the default value is 0
Pass a student if all their scores are >= 50
$isPass = collect($student)
->reduce(function($carry, $item){
return $carry && $item["score"] >= 50;
}, true);
Result: false
Explanation:
- Default value of $carry is true
- If all score is greater than 50, the result will return true; if any less than 50, return false.
Fail a student if any score is < 50
$isFail = collect($student)
->reduce(function($carry, $item){
return $carry || $item["score"] < 50;
}, false);
Result: true
Explain:
- the default value of $carry is false
- if any score is less than 50, return true; if all scores are greater than 50, return false.
Return subject with the highest score
$highestSubject = collect($student)
->reduce(function($carry, $item){
return $carry === null || $item["score"] > $carry["score"] ? $item : $carry;
});
result: [ "subject" => "English", "score" => 61 ]
Explain:
-
The second parameter is not provided in this case.
-
The default value of $carry is null, thus we check for that in our conditional.
