Views topic

For each table you can define a series of Views, which you can query for. A view is a modified subset of fields of the table and resolved relations.

A View is helpful, when you have different points in your application where you want to query the same model, but with different access demands, like privacy.

As an easy example take a typical User model. In the database, you might want to store some public information for a user, like the username, together with some private information, like the address. When a user requests its own data, you want to return all available data, public and private. But when a user requests the information for another user, you want to only return the public information. With stormberry you can handle this automatically by defining separate Views on the User model.

You define Views like this:

@Model(views: [#Complete, #Reduced])
abstract class User {
  @PrimaryKey()
  String get id;

  String get name;
  
  @HiddenIn(#Reduced)
  String get address;

  @ViewedIn(#Complete, as: #Info)
  @HiddenIn(#Reduced)
  List<Post> get posts;
}

@Model(views: [#Base, #Info])
abstract class Post {
  @PrimaryKey()
  String get id;

  String get content;

  @ViewedIn(#Base, as: #Reduced)
  @HiddenIn(#Info)
  User get author;
}

First define all views that you want of a model as a list of symbols. Then you can modify specific fields for a view using these annotations

@HiddenIn(#SomeView) removes the field from the view
@ViewedIn(#SomeView, as: #SomeOtherView) modifies the field to use the specified view of the target type

The above model would result in the following view classes:

class CompleteUserView {
  String id;
  String name;
  String address;
  List<InfoPostView> posts;
}

class ReducedUserView {
  String id;
  String name;
}

class BasePostView {
  String id;
  String content;
  ReducedUserView author;
}

class InfoPostView {
  String id;
  String content;
}

As mentioned before, when you have two-way relations in your models you must use Views to resolve any cyclic dependencies. stormberry can't resolve them for you, however it will warn you if it detects any when trying to migrate your database schema.

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Classes

stormberry package

Views topic