I have a collection of "Tickets", using the random collection utility method I select one from the list. The "Tickets" collection should now remove (or forget) that randomly selected ticket so I can further process that collection. Using the forget method doesn't appear to do what is described in the documentation or (more likely I'm missing something).
Can someone spot whats wrong in my code?
$tickets = Tickets::all();
$total_winners = 5;
$selected_tickets = $tickets->random($total_winners);
$jackpot_winner = $selected_tickets->random();
$selected_tickets->forget($jackpot_winner->id); // this line should remove the $jackpot_winner
When I print the contents of $selected_tickets on lines 3 and lines 5, they have the exact same items, including the $jackpot_winner.
Forget function uses the collection key not the id from the model. To achieve what you want you may use this method:
$selected_tickets = $selected_tickets->except($jackpot_winner->id);
https://laravel.com/docs/8.x/collections#method-except
Related
So I have a set of options that each contain an int value representing their ordinal.
These options are stored in a remote database with each option being a record.
As such when I fetch them from the db I end up with a list of future:
e.g. List<Future<Option>>
I need to be able to sort these Options.
The following dart pad shows a simplified view of what I'm trying to achieve:
https://dartpad.dartlang.org/a5175401516dbb9242a0edec4c89fef6
The Options MUST be futures.
My original solution was to copy the Options into a list, 'complete' them, then sort the list.
This however caused other problems and as such I need to do an 'insitu' sort on the original list.
You cannot sort the futures before they have completed, and even then, you need to extract the values first.
If you need to have a list of futures afterwards, this is what I would do:
List<Future<T>> sortFutures<T>(List<Future<T>> input, [int compare(T a, T b)]) {
var completers = [for (var i = 0; i < input.length; i++) Completer<T>()];
Future.wait(input).then((values) {
values.sort(compare);
for (int i = 0; i < values.length; i++) {
completers[i].complete(values[i]);
}
});
return [for (var c in completers) c.future];
}
This does not return the original futures because you don't know the ordering at the time you have to return them. It does return futures which complete with the same value.
If any of the futures completes with an error, then this blows up. You'll need more error handling if that is possible.
Gentlfolk,
thanks for the help.
julemand101 suggestion of using Future.wait() lead me to the answer.
It also helped me better understand the problem.
I've done a new gist that more accurately shows what I was attempting to do.
Essentilly when we do a db request over the network we get an entity back.
The problem is that the entity will often have references to other entities.
This can end in a whole tree of entities needing to be returned.
Often you don't need any of these entities.
So the solution we went for is to only return the database 'id' of each child entity (only the immediate children).
We then store those id's in a class RefId (see below).
The RefId is essentially a future that has the entities id and knows how to fetch the entity from the db.
When we actually need to access a child entity we force the RefId to complete (i.e. retrieve the entity across the network boundary).
We have a whole caching scheme to keep this performant as well as the ability to force the fetching of child elements, as part of the parent request, where we know up front they will be needed.
The options in my example are essentially menu items that need to be sorted.
But of course I can't sort them until they have been retrieved.
So a re-written example and answer:
https://dartpad.dartlang.org/369e71bb173ba3c19d28f6d6fec2072a
Here is the actual IdRef class we use:
https://dartpad.dartlang.org/ba892873a94d9f6f3924436e9fcd1b42
It now has a static resolveList method to help with this type of problem.
Thanks for your assistance.
I have some instances where a eloquent is resulting an single array not a collection. Although dd shows it as a collection with a single entry.
For example I have a query in a controller:
$pg = Page::with('getPanels')->where('slug',$slug)->get();
This will return a single result and works fine, so I pass this to a blade template. My complete function is
$pg = Page::with('getPanels')->where('slug',$slug)->get();
return view('front.page',['pg' => $pg]);
As soon as he template is brought in it will fall over at
if (!is_null($pg->headImage))
{$img = asset('images/pages')."/".$pg->headImage;}
and I will get
Property [headImage] does not exist on this collection instance.
If I change the line to
if (!is_null($pg[0]['headImage']))
it will continue OK. This is of course a pain as I would much rather use $pg->headImage.
Can someone enlighten me please?
I have sorted this and I hope it will help other people.
If I use
$pg = Page::with('getPanels')->where('slug',$slug)->first();
it will be just one result (naturally) and therefore
$pg->headImage
will fail as it wants
$pg[0]['headImage']
but if I change the eloquent instead of get(0 to first() (still just one result)
$pg = Page::with('getPanels')->where('slug',$slug)->first();
I can use $pg->headImage or what field I want.
Using Laravel 5.3, I have a model with the following function
public function myData() {
return $this->hasMany(MyData::class);
}
and in my collection I have the following
$my_data = MyModel->myData()->get();
All good so far. If I return $my_data I get an eloquent collection with three items.
What I need now though is to create a duplicate of that collection but containing only three of the fields.
I have tried several different things, each of which return an error. The following is the closest I have got, but this returns an empty array - I assume because the fields are located one level deeper than the collection object.
$new_collection = $my_data->only(['field_1', 'field_2', 'field_3']);
What would be the correct way to create a new collection containing all three items, each with only the three selected fields?
Thanks for your help
You could use map:
$slimmed_down = $collection->map(function ($item, $key) {
return [
'field_1' => $item->field_1,
'field_2' => $item->field_2,
'field_3' => $item->field_3
];
});
This will return a new Collection with just the values you want. As far as I know there isn't any other method that does what you want, so iterating over every item and selecting the fields this way is one of the few solutions.
The advantage of using map instead of a standard foreach loop is that when you use map it returns a new instance of Collection.
Edit:
After some thoughts and research about this, the problem you'll have created is that the all the values in the Collection aren't instances of anything anymore. If you don't mind this effect, an even prettier and faster way would be to do this:
$slimmed_down = $collection->toArray()->only(['field_1', 'field_2', 'field_3']);
This basically has the same result.
Using Laravel 9, I just had the same issue :
$my_data->only(['field_1', 'field_2', 'field_3']);
returning an empty array.
I solved it with :
$my_data->map->only(['field_1', 'field_2', 'field_3']);
Here is a very basic example of what I want to do. The code I have come up with seems quite verbose... ie looping through the collection, etc.
I am using a Telerik MVC grid that posts back a collection of deleted, inserted and updated ViewModels. The view models are similar but not exactly the same as the entity.
For example... I have:
Order.Lines. Lines is an entity collection (navigation property) containing OrderDetail records. In the update action of my controller using the I have a List names DeletedLines pulled from the POST data. I also have queried the database and have the Order entity including the Lines collection.
Now I basically want to tell it to delete all the OrderDetails in the Lines EntityCollection.
The way I have done it is something like:
foreach (var line in DeletedLines) {
db.DeleteObject(Order.Lines.Where(l => l.Key == line.Key).SingleOrDefault())
}
I was hoping there was a way that I could use .Interset() to get a collection of entities to delete and pass that to DeleteObject.. however, DeleteObject seems to only accept a single entity rather than a collection.
Perhaps the above is good enough.. but it seemed like there should be an easier method.
Thanks,
BOb
Are the items in DeletedLines attached to the context? If so, what about this?
foreach (var line in DeletedLines) db.DeleteObject(line);
Response to comment #1
Ok, I see now. You can make your code a bit shorter, but not much:
foreach (var line in DeletedLines) {
db.DeleteObject(Order.Lines.SingleOrDefault(l => l.Key == line.Key))
}
I'm not sure if DeleteObject will throw an exception when you pass it null. If it does, you may be even better off using Single, as long as you're sure the item is in there:
foreach (var line in DeletedLines) {
db.DeleteObject(Order.Lines.Single(l => l.Key == line.Key))
}
If you don't want to re-query the database and either already have the mapping table PK values (or can include them in the client call), you could use one of Alex James's tips for deleting without first retrieving:
http://blogs.msdn.com/b/alexj/archive/2009/03/27/tip-9-deleting-an-object-without-retrieving-it.aspx
I'm encountering an issue because I'm sure I'm not doing this correctly with my programming. I have created a custom model in Magento.
In the database table of my model there are several entities with the same attributes...
I need to pick just one from all these entities with the same attribute that I have. For the moment I did this:
$myvariable = Mage::getModel('test/test')->getCollection()
->setOrder('idserialkeys', 'asc')
->addFilter('idproduit', 1)
->addFilter('utilise', 0)
->addFilter('customerid', 0)
->addFilter('numcommande', 0)
From this loading I have around a hundred results but I need to update only one of these, so just after I'm doing:
->setPageSize(1);
The problem is that I need a foreach after to update my entity
foreach($mavaribale as $modifiemoi) {
// Update of my entity because of course there is only one
}
As you can see I'm obliged to do a loop (for each) even if I have a setPagesize... I would like to avoid this loop to optimize my code.
When you have a collection, and you only need one element, use the getFirstItem method. Try this:
$modifiemoi = $myvariable->getFirstItem();
Make sure that you also use your setPageSize call so that you only transfer data for one item.
All collections are Varien_Data_Collection objects so you can use getFirstItem:
$modifiemoi = $mavaribale->getFirstItem();