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Lazy Initialization in Swift

Swift, Lazy Initialization, Performance1 min read

In software development, lazy initialization is a technique that defers the creation of an object until it's actually needed. The idea behind this technique is to improve performance and reduce memory usage by only creating an object when it is needed and not before. In this article, we'll dive into what lazy initialization is, why it's important, and how to use it in Swift.

Why Use Lazy Initialization in Swift?

Lazy initialization can be especially useful in Swift, where the cost of object creation can be quite high. For example, if you have a large object that takes a long time to initialize, you may only want to create it when it's actually needed, instead of creating it upfront. This can help improve performance and reduce memory usage. Additionally, lazy initialization can also help you avoid unnecessary initialization errors, as you can perform any necessary checks when the object is actually needed.

How to Use Lazy Initialization in Swift?

Lazy initialization in Swift is quite simple to use. You can use the lazy keyword in front of a property to make it lazy. When a lazy property is first accessed, it's created, and then it's stored for future use. For example:

1class SomeClass {
2 lazy var someProperty: SomeType = {
3 return SomeType()
4 }()

In this example, someProperty is a lazy property of type SomeType. When someProperty is first accessed, the closure is executed, and the result of the closure is stored as the value of someProperty. From that point on, the value of someProperty is available for future use.

It's important to note that the closure used to initialize a lazy property is only executed once, even if the property is accessed multiple times. This makes it an efficient way to initialize an object, as the object is only created once, and then stored for future use.

Another important aspect of lazy initialization is that it is thread-safe. This means that multiple threads can access a lazy property at the same time, and only one instance of the object will be created, even if multiple threads are trying to access it simultaneously.


Lazy initialization is a useful technique for improving performance and reducing memory usage in Swift. By deferring the creation of an object until it's actually needed, you can avoid creating objects that may never be used. Additionally, lazy initialization is simple to use and is thread-safe, making it a great choice for your Swift projects.