Weak cache is a Map implementation that uses WeakReferences for holding values and Finalizer to manage it's storage.

You can use this to cache data for a small amount of time until next garbage collection cycle.

Note: Values cannot be numbers, strings, booleans, records, null, dart:ffi pointers, dart:ffi structs, or dart:ffi unions.

• Uses WeakReference for storing values.
• Uses Finalizer to remove objects from internal storage upon their deletion.
• Allows you iterate over keys/values.

  While iterating, all stored values are temporarily made into strong references, to prevent concurrent edit of storage, while iterating over it.

• Optimized containsValue via internal managed Expando.
• Implements full Map<K, V> interface.
• WeakCache itself can be safely garbage collected and doesn't hold unto any stored data.

Create cache, add values, and they'll be removed once there no more strong references to them.

// ID - Object cache
final cache = WeakCache<int, Object>();

Object? obj = Object();
cache[0] = obj;
// ...
obj = null;
// ...
// After garbage collection cache[0] will be removed.
cache[0] == null;

See example for detailed test case.