Swift: Master Strong, Weak, & Unowned References for Optimal Code
If you’re a Swift programmer, you’ve probably come across the terms strong, weak, and unowned references. But what do these terms mean? How do they differ from one another? And most importantly, when should you use which reference type?
In this blog post, we’ll explore the differences between strong, weak, and unowned references in Swift. We’ll discuss the benefits of each reference type and look at examples of when you should use each reference type. By the end of this post, you’ll have a better understanding of how to use strong, weak, and unowned references in your Swift code.
What Are Strong, Weak, and Unowned References?
Before we dive into the differences between strong, weak, and unowned references, let’s quickly define each term.
Strong Reference
A strong reference is a reference that keeps a strong hold on the object it references. This means that as long as the strong reference is held, the object will not be deallocated from memory.
let strongReference = SomeClass()In this example, we create a strong reference to an instance of SomeClass. This reference will keep the instance alive in memory as long as the reference is held.
Weak Reference
A weak reference is a reference that does not keep a strong hold on the object it references. This means that if the only references to an object are weak references, the object will be deallocated from memory.
weak var weakReference: SomeClass?In this example, we create a weak reference to an instance of SomeClass. This reference will not keep the instance alive in memory, so if all other references are gone, the instance will be deallocated from memory.
Unowned Reference
An unowned reference is similar to a weak reference, except that it does not need to be optional. This means that the object referenced by an unowned reference is guaranteed to exist in memory.
unowned let unownedReference = SomeClass()In this example, we create an unowned reference to an instance of SomeClass. This reference does not keep the instance alive in memory, but it is guaranteed to exist in memory as long as the reference is held.
When Should You Use Each Reference Type?
Now that we know what strong, weak, and unowned references are, let’s look at when you should use each reference type.
Strong Reference
You should use a strong reference when you want to keep an object alive in memory for as long as the reference is held. This is the default reference type in Swift, so you don’t need to explicitly declare it.
Weak Reference
You should use a weak reference when you want to allow an object to be deallocated from memory if there are no other references to it. This is useful in cases where you have a circular reference (e.g., two objects referencing each other) or when you don’t want to keep an object alive for the lifetime of the reference.
Unowned Reference
You should use an unowned reference when you want to guarantee that an object exists in memory for the lifetime of the reference. This is useful in cases where you have a one-to-one relationship between two objects (e.g., a parent-child relationship) and you don’t want the child to outlive the parent.
Conclusion
In this blog post, we explored the differences between strong, weak, and unowned references in Swift. We discussed the benefits of each reference type and looked at examples of when you should use each reference type. Now you should have a better understanding of how to use strong, weak, and unowned references in your Swift code.