https://github.com/realm/realm-dotnet-groupedcollection

https://github.com/realm/realm-dotnet-groupedcollection

Last synced: 23 days ago
JSON representation

• Host: GitHub
• URL: https://github.com/realm/realm-dotnet-groupedcollection
• Owner: realm
• License: mit
• Created: 2017-06-29T11:03:48.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2017-08-23T14:32:44.000Z (over 7 years ago)
• Last Synced: 2024-11-08T20:08:36.576Z (about 1 month ago)
• Language: C#
• Size: 10.7 KB
• Stars: 8
• Watchers: 7
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-realm - GroupedCollections - Data bindable grouped collections that can be passed directly to a Xamarin.Forms ListView. (<a name="dotnet"> .Net & Unity / <a name="dotnet-libs"></a>.Net Libraries and Components)

README

        
# GroupedRealmCollection

A set of extension methods that can project [Realm Xamarin](https://realm.io/docs/xamarin/latest/) collections

to data bindable grouped collections that can be passed directly to a [Xamarin.Forms](https://www.xamarin.com/forms) ListView.

## Getting started

Just add the [Realm.GroupedCollection](https://www.nuget.org/packages/Realm.GroupedCollection) package to your project.

## Sample usage

```csharp

// In your ViewModel

Students = realm.All().ToGroupedCollection(school => school.Students);

```

This can then be passed to your ListView:

```xml

    

        

            

        

    

```

And your models would look something like:

```csharp

class Student : RealmObject

{

    public string Name { get; set; }

    

    public School School { get; set; }

}

class School : RealmObject

{

    public string Name { get; set; }

    

    [Backlink(nameof(Student.School))]

    public IQueryable Students { get; }

}

```

## Features

Both the returned collection and the inner collections are observable, so any changes will update the UI.

### Queries

```csharp

// Return schools ordered by Name, containing Students ordered by Age

var students = realm.All().OrderBy(school => school.Name)

                    .ToGroupedCollection(school => school.Students.OrderBy(student => student.Age));

```

Supported query operations are limited by [Realm's query support](https://realm.io/docs/xamarin/1.5.0/api/linqsupport.html).

### [To-many relationships](https://realm.io/docs/xamarin/latest/#to-many-relationships)

```csharp

public class Dog : RealmObject

{

    public string Name { get; set; }

}

public class Person : RealmObject 

{

    public IList Dogs { get; } 

}

var dogs = realm.All().ToGroupedCollection(person => person.Dogs);

```

Note that queries over `IList` properties are not supported and will result in a runtime exception. This is the

case because those queries are executed by LINQ and not by Realm itself.

## Using Backlinks to invert the group direction

Usually, a .NET grouping would go from the specific to the general:

```csharp

IEnumerable students = ...;

var groupedStudents = students.GroupBy(s => s.School);

```

Since Realm doesn't yet support grouping, we can achieve the same result by using [backlinks (inverse relationships)](https://realm.io/docs/xamarin/latest/#inverse-relationships).

Then, the grouping goes from the general to the specific:

```csharp

IQueryable schools = realm.All();

var groupedStudents = schools.ToGroupedCollection(s => s.Students);

```

## License

This project is released under the [MIT license](https://github.com/realm/realm-dotnet-groupedcollection/blob/master/LICENSE).