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Function to build associative arrays from an input list and two user functions producing keys and values for the output list #164
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create_assoc? Anw, what might be a use case for this?@phanan Sorry, I messed up explaining what I want.
Basically what I suggest is an analogue to Yii2's
ArrayHelpers::map. It doesn't do whatmapdoes in functional programming (i.e. taking a list and returning another list), but rather it takes:- an input list
- a function to produce keys of the output list
- a function to produce values of the output list
and creates an associative array (a map) from the keys to values for the same elements of the original array, e.g.:
ArrayMap::map( [ ['id' => 1, 'name' => 'Bob'], ['id' => 2, 'name' => 'Joj'], ['id' => 3, 'name' => 'Yoy'], ], function($elem, $index) { return $elem['id']; }, function($elem, $index) { return 'Mister '.$elem['name']; } ); /* returns [ 1 => 'Mister Bob', 2 => 'Mister Joj', 3 => 'Mister Yoy' ] */
Example: I have a list of books. I need to get a map from book ids to their names to pass to a view to render a
<select>elementIn plain PHP:
$ids2Names = []; foreach ($books as $book) { $ids2Names[$book->id] = $book->name; }
With
ArrayHelper::mapfrom Yii2:ArrayHelper::map( $books, function($book) { return $book->id; }, function($book) { return $book->name; } );
With
create_assoc:create_assoc( $books, function($book) { return $book->id; }, function($book) { return $book->name; } );
Benefit of this approach in comparison to plain php is that it is more semantical and isolates logic for getting keys and values, doesn't require you to come up with the assotiative array name. We can also add a check that no two entries of the input array produce the same key.
array_combine(map(…, …), map(…, …))is not good enough?array_combine( map($books, function($book) { return $book->id; }), map($books, function($book) { return $book->name; }) );
vs
create_assoc( $books, function($book) { return $book->id; }, function($book) { return $book->name; } );
Also if we want to do something like this:
create_assoc( filter( $bookRepository->getBooks(), function() { // maybe some more logic } ), function($book) { return $book->id; }, function($book) { return $book->name; } );
then in the
array_combine()case we'll have to use an extra variable.Also
mapand the input array are not written twice increate_assoc. Also usingcreate_assocwould explicitly state the relation between keys and values, unlikearray_combinewhere you'd have to parse it visually. I think functional-php has many functions that are much more niche than this one, and ability to create associative arrays easily to me seems to be an essential but missing piece of this library ($preserveKeyseverywhere).Personally, I don't see a big gain :/ Btw, your
create_assoc's example should have been written this way for a fairer comparison:create_assoc( $books, function($book) { return $book->id; }, function($book) { return $book->name; } );
As you can see,
create_associs one LoC longer ;)@phanan It is not about LoC, it is about the amount of nested expressions ;;;)))
Btw, if you rewrite my
create_assocexample, then consider doing the same forarray_combine:array_combine( map( $books, function($book) { return $book->id; } ), map( $books, function($book) { return $book->name; } ) );
Ok, let's wait several months till the few people who haven't already searched for a less verbose way to build associative arrays in PHP start upvoting this coming via Google, if you don't think this suggestion is useful.
- changed the title
[-]Function to build associative arrays from a list of keys and a function to produce its values[/-][+]Function to build associative arrays from an input list and two user functions producing keys and values for the output list[/+]on Jul 6, 2018 Another option that came to mind was to use reindex:
map( function ($book) { return $book->name; }, reindex( function($book) { return $book->id; }, filter($collection, …) ) )But I like that the
create_assocreads so well. Let me ponder this a bit longerWhat do you think about unfold?
https://github.com/apantle/fun-php/blob/master/README.md#unfoldIt does already what you are looking for, if the passed function is unary is called with just the input as argument, and allows optional values or even a helper to pass around values between applied functions.
We use it to apply a bunch of different service calls to a single entry, like a tap but calling many functions to build a single assoc array.
Happy to merge this little function of mine with more tests and a better suited name to the project.
So @gvlasov, my proposal it very similar to what you have requested, but instead of directly building the associative array, instead I'm returning a function that allow to build any number of associative arrays, based on the same set of rules with a single or a series of input values.
If there are some issues on my proposal, please let me know to make it more useful. My tests are copied from the independent project I've worked this function, and they are thought more closely to a complement of another library that I use to map associative arrays, reducing them being a common case. This function makes the opposite, that's why in the little collection I've built I called it originally
unfold.
This is a feature request. Something like this:I'm not sure what that function would be called, I admit that it should have a better name thancreate_mapCouldn't properly explain what I want in the original post, see a comment below: #164 (comment)