ValueWrapper class final

A value found in a cache, wrapped so that a stored null can be told apart from a missing entry.

Cache.get returns a ValueWrapper for a hit and null for a miss. Without the wrapper a method whose result was null would look uncached and run again every time. You meet it when you read a cache by hand or write a Cache of your own: return ValueWrapper(value) for a hit (also when value is null) and null for a miss.

// An admin page shows what is cached for one isbn.
final wrapper = cacheManager.getCache('books')!.get('978-0');
if (wrapper != null) {
  log.info(wrapper.value); // may be null: null was cached
}

Spring (Java):

Cache.ValueWrapper wrapper = cache.get("978-0");
if (wrapper != null) log.info("{}", wrapper.get());

Constructors

ValueWrapper(Object? value)

Wraps value, which may be null.

const

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

value → Object?

The cached value; null when null was stored.

final

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited