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core/WeakReference

Module that implements a weak reference to an object.

ATTENTION: This functionality does not work with classical persistence (--legacy-persistence moc flag).

Usage example: Import from the core package to use this module.

import WeakReference "mo:core/WeakReference";

Type WeakReference​

type WeakReference<T> = { ref : weakT }

Function allocate​

func allocate<T>(obj : T) : WeakReference<T>

Allocate a new weak reference to the given object.

The obj parameter is the object to allocate a weak reference for. Returns a new weak reference pointingto the given object.

let obj = { x = 1 };
let weakRef = WeakReference.allocate(obj);

Function get​

func get<T>(self : WeakReference<T>) : ?T

Get the value that the weak reference is pointing to.

The self parameter is the weak reference pointing to the value the function returns. The function returns the value that the weak reference is pointing to, or null if the value has been collected by the garbage collector.

let obj = { x = 1 };
let weakRef = WeakReference.allocate(obj);
let value = weakRef.get();

Function isLive​

func isLive<T>(self : WeakReference<T>) : Bool

Check if the weak reference is still alive.

The self parameter is the weak reference to check whether it is still alive. Returns true if the weak reference is still alive, false otherwise. False means that the value has been collected by the garbage collector.

let obj = { x = 1 };
let weakRef = WeakReference.allocate(obj);
let isLive = weakRef.isLive();
assert isLive == true;