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This article will explain in detail how to recycle weakreference. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

In computer programming, weakreference weak references, as opposed to strong references, are references that cannot be guaranteed that the objects they reference will not be reclaimed by the garbage collector. An object that is referenced only by a weak reference is considered inaccessible (or weakly accessible) and may therefore be recycled at any time. Some languages with garbage collection mechanisms, such as Java, C #, Python, Perl, Lisp, and so on, support weak references to varying degrees.

Weakreference garbage collection

Garbage collection is used to clean up objects that will no longer be used, thereby reducing the possibility of memory leaks and data corruption. There are two main types of garbage collection: tracking and reference counting. Reference count records the number of references to a given object and collects the object when the number of references is 00:00. Because only one object can be recycled at a time, reference counting cannot recycle objects referenced by a loop. A set of objects that refer to each other will survive forever if they are not directly referenced by other objects and are not accessible. If an application continues to produce such inaccessible groups of objects, a memory leak will occur. Using weak references within an object group (that is, references that are not counted in the reference count) can sometimes avoid reference rings, so weak references can be used to solve the problem of circular references. For example, Apple's Cocoa framework recommends this method, specifically, using strong references in parent-to-child references and weak references in child-to-parent references, thus avoiding circular references.

Programs only make weak references to some objects, which can be used to indicate which objects are unimportant, so weak references are also used to minimize the number of unnecessary objects in memory.

Weakreference variety

Some languages contain weak references of multiple strengths. Java, for example, defines soft references, weak references, and virtual references, with the strength of references decreasing in turn. Each citation has a corresponding concept. The garbage collector (GC) determines when an object is reclaimed by determining its accessibility type. When an object is soft accessible, the garbage collector can safely reclaim the object, but if the garbage collector believes that JVM still has free memory (for example, JVM has a lot of unused heap space), it may not immediately recycle soft accessible objects. But for weakly accessible objects, once noticed by the garbage collector, they are reclaimed. Unlike other types of references, virtual references cannot be tracked. On the other hand, virtual references provide a mechanism for programs to be notified when an object is reclaimed. Some languages that do not have a garbage collection mechanism, such as garbage collection, also provide strong / weak references as support for garbage collection libraries. In C++, ordinary pointers can be seen as weak references, while smart pointers can be seen as strong references, although pointers are not "really" weak references, because weak references should know when objects become inaccessible.

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