Selectable<T> class abstract mixin

Abstract class for queries which can return one-time values or a stream of values.

If you want to make your query consumable as either a Future or a Stream, you can refine your return type using one of Selectable's base classes:

/// Retrieve a page of [Todo]s.
MultiSelectable<Todo> pageOfTodos(int page, {int pageSize = 10}) {
  return select(todos)..limit(pageSize, offset: page);
}
pageOfTodos(1).get();
pageOfTodos(1).watch();

// Retrieve a todo known to exist.
SingleSelectable<Todo> entryById(int id) {
  return select(todos)..where((t) => t.id.equals(id));
}
final idGuaranteedToExist = 10;
entryById(idGuaranteedToExist).getSingle();
entryById(idGuaranteedToExist).watchSingle();

// Retrieve a todo from an external link that may not be valid.
SingleOrNullSelectable<Todo> entryFromExternalLink(int id) {
  return select(todos)..where((t) => t.id.equals(id));
}
final idFromEmailLink = 100;
entryFromExternalLink(idFromEmailLink).getSingleOrNull();
entryFromExternalLink(idFromEmailLink).watchSingleOrNull();

Implemented types

• MultiSelectable<T>
• SingleSelectable<T>
• SingleOrNullSelectable<T>

Implementers

• CustomSelectStatement
• JoinedSelectStatement
• SimpleSelectStatement

Constructors

Selectable()

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

asyncMap<N>(FutureOr<N> mapper(T)) → Selectable<N>

Maps this selectable by the mapper function.

get() → Future<List<T>>

Executes this statement and returns the result.

override

getSingle() → Future<T>

Executes this statement, like Selectable.get, but only returns one value. the query returns no or too many rows, the returned future will complete with an error.

override

getSingleOrNull() → Future<T?>

Executes this statement, like Selectable.get, but only returns one value. If the result too many values, this method will throw. If no row is returned, null will be returned instead.

override

map<N>(N mapper(T)) → Selectable<N>

Maps this selectable by the mapper function.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

watch() → Stream<List<T>>

Creates an auto-updating stream of the result that emits new items whenever any table used in this statement changes.

override

watchSingle() → Stream<T>

Creates an auto-updating stream of this statement, similar to Selectable.watch. However, it is assumed that the query will only emit one result, so instead of returning a Stream<List<T>>, this returns a Stream<T>. If, at any point, the query emits no or more than one rows, an error will be added to the stream instead.

override

watchSingleOrNull() → Stream<T?>

Creates an auto-updating stream of this statement, similar to Selectable.watch. However, it is assumed that the query will only emit one result, so instead of returning a Stream<List<T>>, this returns a Stream<T?>. If the query emits more than one row at some point, an error will be emitted to the stream instead. If the query emits zero rows at some point, null will be added to the stream instead.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited