parse gives this example...
Internally, the Parse framework will store the referred-to object in
just one place, to maintain consistency. You can also link objects
using just their objectIds like so:
var post = new Post();
post.id = "1zEcyElZ80";
myComment.set("parent", post);
say i want to link a new comment to an existing post, how would i go about this? given i have the post objectId.
Ian, unless that target page was edited, your answer is incorrect. As per that page:
A good rule of thumb is, use a pointer for a one-to-one or one-to-many
relationship. Use a relation when you have a many-to-many
relationship.
It would seem there is some fuzziness in this area that many are not happy about.
Like I said in my comment, I prefer to set it up before hand in the parse data browser, but you would want to use a relation between the post and the comment not a pointer as I previously stated.
This is because a pointer should be used for a one-to-one relationship and a relation for a one-to-many relationship as a comment would be to a post.
https://parse.com/questions/pointer-vs-relation
This is in Java using Pointers to build relationship.
ParseObject favorite = new ParseObject("favorite");
myComment.put("parent", ParseObject.createWithoutData("post_id", "1zEcyElZ80"));
myComment.saveInBackground();
Related
I have a variable $courses that in my debugger is shown as type App/Courses
In the model, there is a one to many relation and I retrieve these related items in the model and then access as $courses->relateditems
In the debugger, $courses->relateditems is shown as type Illuminate/Database/Eloquent/Collection
Ok, all makes sense.
I want to get last item in the $courses->relateditems collection. So I try
$courses->relateditems->last()->startdate
But this is not returning the value that I know exists. And when I evaluate the expression $courses->relateditems->last() in the debugger I get this in my laravel.log:
Symfony\Component\Debug\Exception\FatalErrorException: Cannot access self:: when no class scope is active in /app/Courses.php:68
I am just not sure what is going on. I know I can use DB queries to just get the data I need, but I have a model event triggering a function and that function receives the $courses object/model (or however we name it) and I am just trying to get this working as above.
Ideas on what I am doing wrong?
thanks,
Brian
The issue here based on the error you have at the bottom of your post is a mistake in your code.
However, I think you've misunderstood how Laravel relationships work. They essentially come in two forms on a model, that of a property and that of a method.
relateditems Is a magic property that will return the result of a simple select on the relationship if one has already been performed. If one hasn't been performed it will perform one and then return it, known as eager loading.
relateditems() Is a method that returns a query builder instance for that relationship.
By calling relateditems->last() you're loading ALL related items from the database and then getting the last, which is less than optimal.
The best thing for you to do is this:
$course->relateditems()->orderBy('id', 'desc')->first();
This will get the first item return, however, since we've ordered it by id in descending order, it'll be reversed from what could be considered its default ordering. Feel free to change the id to whatever you want.
I'm trying to get data from an Eloquent query as follows:
$submission->find($id)->first()->with('user', 'clientform')->get();
I'm sending the submission to the view and attempting to access properties from the user model like so:
{{ $submission->clientform->name }}
However, Laravel is throwing the following error:
Undefined property: Illuminate\Database\Eloquent\Collection::$clientform
What am I doing wrong with the way my query is formatted?
You're overdoing it!
Let's break it down:
$submission->find($id);
Will return an instance of the model which corresponds to the entry having the primary key of $id.
$submission->find($id)->first();
This is an unncessary repetition; the find method already gives you a single entry, no need to call first on it.
$submission->find($id)->first()->with('user', 'clientform');
This is where you start going the wrong way; when calling with on a model, Laravel will transform that model into a query builder again, even though it was already resolved by calling find.
$submission->find($id)->first()->with('user', 'clientform')->get();
Finally, the get method resolves the builder into a Illuminate\Support\Collection, regardless of the number of entries found (i.e. it could be a Collection of only one item). It's worth noting, though, that your query will most likely have been fully reset by calling with. It would be the same as instantiating a fresh Submission model and building your query with it. That means you're probably using a collection of all your submission entries, not just the one with $id.
Long story short, this is what you want:
$submission->with('user', 'clientform')->find($id);
It will fetch the matching $id, with the user and clientform relations eager-loaded.
I've got a function in my User model (I use Laravel's default User model) that is a relationship with the Player model.
I want to retrieve the id of the Player, but I can't. Is there anyway to do it? I've tried something like:
Auth::user()->players->id;
or
Auth::user()->id->players;
but it doesn't work. Any hints?
That depends on the type of your relationship. From the code you provided I can guess that the relationship is called 'players' and not 'player' (meaning you should have a players() function inside your User model). If this is the case, than your code
Auth::user()->players
returns a collections of players. You can loop through this collection and get IDs of the players:
foreach (Auth::user()->players as $player)
{
$playerId = $player->id;
// Do more stuff for a single player here
}
Hope this clarifies things a little bit. If not, please provide more details about your relationship between User and Player models.
You can also find more details here: http://laravel.com/docs/eloquent#relationships
If I want to create a entity in Core Data that has attributes with values that should be localizable I'm wondering how the most efficient way would look like?
As a example let's assume the following structure:
Book
name (localizable)
description (localizable)
author
An localized book entry would look like this:
name: "A great novel" (en/international),
"Ein großartiger Roman" (de),
"Un grand roman" (fr)
description:
"Great!" (en/international),
"Großartig!" (de),
"Grand!" (fr)
author: "John Smith"
In a SQL/SQLite implementation I would use two tables. A books table containing the book information (author, the english/international name and description) and the localizationBooks table that is related using the primary key of the corresponding book. This second table contains the localized name and description values as well as the languageCode. This would allow to have a scalable number of localizations.
For fetching the data I would use a
SELECT COALESCE(localizationBooks.name, books.name)
to get the actual values for the given language code. This allows to use the international english value as fallback for unsupported languages.
Would this require a separate entity in Core Data (e.g. BookLocalization) that has a relation to the Book or is there another recommended way of doing this?
The strategy you mention is usually the best. As you suggest, this requires an extra entity for the localized properties.
You can then write a helper method on your Books entity to get the appropriate localization object for a given language and use it like this:
[book bookLocalizationForLanguage:#"de"].name
You could even take it a step further and just add properties like localizedName, localizedDescription on the Books entity which will fetch the appropriate localized value.
Well, despite that this topic is 3 years old... I just stumbled upon it, asking my self the very same as the original poster. I found another thread with an answer.
I'll just repeat it in here in case somebody else hits this thread (Answer from Gordon Hughes):
Good practices for multiple language data in Core Data
To summarize:
Let's say you have Entity Books. Then you will have to make an additional one, called Localizedbook for example. In Books you have the attribute "title" and in LocalizedBook you have "localizedTitle" and "locale" for international strings like "en_US".
You now have to set the relationship between title -> localizedTitle (one to many, as one original title can have multiple translations).
So, every time you fetch "title" you will get the "localizedTitle" given to a specific locale, if the relations are set correctly.
Okay, so I'm doing my first foray into using the ADO.NET Entity Framework.
My test case right now includes a SQL Server 2008 database with 2 tables, Member and Profile, with a 1:1 relationship.
I then used the Entity Data Model wizard to auto-generate the EDM from the database. It generated a model with the correct association. Now I want to do this:
ObjectQuery<Member> members = entities.Member;
IQueryable<Member> membersQuery = from m in members select m;
foreach (Member m in membersQuery)
{
Profile p = m.Profile;
...
}
Which halfway works. I am able to iterate through all of the Members. But the problem I'm having is that m.Profile is always null. The examples for LINQ to Entities on the MSDN library seem to suggest that I will be able to seamlessly follow the navigation relationships like that, but it doesn't seem to work that way. I found that if I first load the profiles in a separate call somehow, such as using entities.Profile.ToList, then m.Profile will point to a valid Profile.
So my question is, is there an elegant way to force the framework to automatically load the data along the navigation relationships, or do I need to do that explicitly with a join or something else?
Thanks
Okay I managed to find the answer I needed here http://msdn.microsoft.com/en-us/magazine/cc507640.aspx. The following query will make sure that the Profile entity is loaded:
IQueryable<Member> membersQuery = from m in members.Include("Profile") select m;
I used this technique on a 1 to many relationship and works well. I have a Survey class and many questions as part of that from a different db table and using this technique managed to extract the related questions ...
context.Survey.Include("SurveyQuestion").Where(x => x.Id == id).First()
(context being the generated ObjectContext).
context.Survey.Include<T>().Where(x => x.Id == id).First()
I just spend 10mins trying to put together an extention method to do this, the closest I could come up with is ...
public static ObjectQuery<T> Include<T,U>(this ObjectQuery<T> context)
{
string path = typeof(U).ToString();
string[] split = path.Split('.');
return context.Include(split[split.Length - 1]);
}
Any pointers for the improvements would be most welcome :-)
On doing a bit more research found this ... StackOverflow link which has a post to Func link which is a lot better than my extension method attempt :-)