FutureOr< T> class
A type representing values that are either Future<T>
or T
.
This class declaration is a public stand-in for an internal future-or-value generic type. References to this class are resolved to the internal type.
It is a compile-time error for any class to extend, mix in or implement
FutureOr
.
Note: the FutureOr<T>
type is interpreted as dynamic
in non strong-mode.
Examples
// The `Future<T>.then` function takes a callback [f] that returns either
// an `S` or a `Future<S>`.
Future<S> then<S>(FutureOr<S> f(T x), ...);
// `Completer<T>.complete` takes either a `T` or `Future<T>`.
void complete(FutureOr<T> value);
Advanced
The FutureOr<int>
type is actually the "type union" of the types int
and
Future<int>
. This type union is defined in such a way that
FutureOr<Object>
is both a super- and sub-type of Object
(sub-type
because Object
is one of the types of the union, super-type because
Object
is a super-type of both of the types of the union). Together it
means that FutureOr<Object>
is equivalent to Object
.
As a corollary, FutureOr<Object>
is equivalent to
FutureOr<FutureOr<Object>>
, FutureOr<Future<Object>>
is equivalent to
Future<Object>
.
Properties
- hashCode → int
-
The hash code for this object. [...]
read-only, inherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited
Methods
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed. [...]
inherited
-
toString(
) → String -
Returns a string representation of this object.
inherited
Operators
-
operator ==(
dynamic other) → bool -
The equality operator. [...]
inherited