Associative Array Recipes

Working with associative arrays requires more than just transforming values. This guide shows you how to manipulate both keys and values using the library's functional patterns.

The Key Manipulation Pattern

To modify array keys, use this three-step pattern:

tuples() - Convert to [key, value] pairs
map() - Transform the pairs
unpack() - Reconstruct the array

Prefixing Keys

Add a prefix to all keys in an associative array:

use function Pipeline\take;

$data = ['id' => 123, 'name' => 'Alice', 'status' => 'active'];

$result = take($data)
    ->tuples()
    ->map(fn($tuple) => ['user_' . $tuple[0], $tuple[1]])
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

// Result:
// [
//     'user_id' => 123,
//     'user_name' => 'Alice',
//     'user_status' => 'active'
// ]

Swapping Keys and Values

Flip keys and values, similar to array_flip():

$data = ['a' => 1, 'b' => 2, 'c' => 3];

$result = take($data)
    ->tuples()
    ->map(fn($tuple) => [$tuple[1], $tuple[0]])
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

// Result: [1 => 'a', 2 => 'b', 3 => 'c']

Filtering by Key

Remove entries based on their keys:

$data = ['user_id' => 1, 'password' => 'secret', 'email' => 'alice@example.com'];

$safe = take($data)
    ->tuples()
    ->filter(fn($tuple) => $tuple[0] !== 'password')
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

// Result: ['user_id' => 1, 'email' => 'alice@example.com']

Transforming Keys and Values

Apply different transformations to keys and values:

$data = ['first_name' => 'alice', 'last_name' => 'smith'];

$result = take($data)
    ->tuples()
    ->map(fn($tuple) => [
        str_replace('_', '-', $tuple[0]),  // kebab-case keys
        ucfirst($tuple[1])                 // capitalize values
    ])
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

// Result: ['first-name' => 'Alice', 'last-name' => 'Smith']

Advanced Patterns

Merging with Defaults

Ensure all required keys exist with default values:

$defaults = ['name' => 'Unknown', 'age' => 0, 'active' => true];
$input = ['name' => 'Bob', 'age' => 25];

$result = take($defaults)
    ->tuples()
    ->map(function($tuple) use ($input) {
        [$key, $default] = $tuple;
        return [$key, $input[$key] ?? $default];
    })
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

// Result: ['name' => 'Bob', 'age' => 25, 'active' => true]

Grouping by Key Pattern

Group data by a key pattern:

$data = [
    'user_name' => 'Alice',
    'user_email' => 'alice@example.com',
    'order_id' => 123,
    'order_total' => 99.99
];

$grouped = take($data)
    ->tuples()
    ->fold([], function($groups, $tuple) {
        [$key, $value] = $tuple;
        $prefix = explode('_', $key)[0];
        $groups[$prefix][$key] = $value;
        return $groups;
    });

// Result:
// [
//     'user' => ['user_name' => 'Alice', 'user_email' => 'alice@example.com'],
//     'order' => ['order_id' => 123, 'order_total' => 99.99]
// ]

Performance Considerations

The tuples -> map -> unpack pattern creates intermediate arrays. For large associative arrays, consider using stream() first to process entries one at a time:

$result = take($largeArray)
    ->stream()
    ->tuples()
    ->map(fn($tuple) => ['prefix_' . $tuple[0], $tuple[1]])
    ->unpack(fn($key, $value) => yield $key => $value)
    ->toAssoc();

Pipeline Laravel Package