What Is ARC in Data Structure?


Heather Bennett

What Is ARC in Data Structure?

When it comes to managing memory in data structures, one important concept to understand is ARC (Automatic Reference Counting). ARC is a memory management technique used in programming languages like Objective-C and Swift. It helps automatically manage the allocation and deallocation of memory by keeping track of references to objects.

How Does ARC Work?

ARC works by keeping track of the number of references to an object. Each time a reference to an object is created, the reference count for that object is incremented.

When a reference goes out of scope or is no longer needed, the reference count is decremented. When the reference count reaches zero, meaning there are no more references to the object, the memory occupied by that object is deallocated.

This automatic management of memory helps prevent common issues like memory leaks and dangling pointers. With ARC, developers can focus more on writing code rather than manually managing memory.

Strong References

In ARC, there are two types of references: strong references and weak references. By default, when you create a reference to an object, it creates a strong reference. A strong reference increases the reference count for an object and keeps it alive as long as there is at least one strong reference to it.

Note: It’s essential to be mindful of strong reference cycles where objects hold onto each other through strong references, causing circular dependencies and preventing objects from being deallocated.

Weak References

To avoid strong reference cycles and potential memory leaks, weak references come into play. A weak reference does not increase the reference count of an object and does not keep it alive. If all remaining references to an object are weak references, then the object will be deallocated automatically.

Weak references are commonly used when there is a need for a temporary or optional reference to an object. They are also useful in scenarios where there is a potential for strong reference cycles.

Using ARC in Practice

When working with ARC, it’s important to understand how object ownership affects memory management. By default, objects are created with strong references, but you can explicitly declare weak references using the weak keyword in languages like Swift.


  • In Objective-C: @property (nonatomic, weak) NSObject *weakObject;
  • In Swift: weak var weakObject: NSObject?

It’s crucial to balance strong and weak references carefully to avoid memory leaks and other memory-related issues. Understanding the lifecycle of objects and managing their references appropriately is essential for efficient memory management.


Arc (Automatic Reference Counting) is a powerful memory management technique that helps automate the allocation and deallocation of memory in programming languages like Objective-C and Swift. By keeping track of references to objects, ARC ensures that memory is efficiently managed without manual intervention. Understanding strong and weak references, along with their appropriate use, is vital for effective use of ARC and preventing common memory-related issues.

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