A Quick Guide to Lazy Properties in Swift

In Swift, properties are a fundamental concept, allowing you to store and retrieve values within a class or structure. While most properties are eagerly initialized when an instance is created, Swift provides a mechanism to delay the initialization of properties until they are first accessed. These are known as “lazy properties.” In this quick guide, we will explore what lazy properties are, why you might use them, and how to implement them in your Swift code.

Table of Contents

  1. Introduction
    • An overview of lazy properties and their importance in Swift.
  2. Understanding Lazy Properties
    • Detailed explanation of what lazy properties are and how they differ from regular properties.
  3. Why Use Lazy Properties?
    • Explore scenarios where lazy properties are beneficial and why you’d want to defer property initialization.
  4. Declaring Lazy Properties
    • How to declare and initialize lazy properties in your Swift code.
  5. Use Cases
    • Real-world examples of when and how to use lazy properties in practical scenarios.


In Swift, properties can hold values, but sometimes, you may not want to initialize a property until it’s actually needed. Lazy properties provide a solution to this by delaying initialization until the first time they are accessed. This can lead to more efficient memory usage and improved performance in your Swift applications.

Understanding Lazy Properties

Lazy properties are properties that are only initialized when they are first accessed. This means that their values are not set when an instance is created but instead are calculated or loaded when needed. Lazy properties are useful when you have properties that might not be used during the entire lifecycle of an object or require time-consuming initialization.

Why Use Lazy Properties?

Lazy properties offer several advantages, including:

  • Efficiency: They can improve your app’s efficiency by postponing the initialization of properties until they are actually needed. This can save memory and processing power.
  • Circular References: Lazy properties can help avoid circular references in your code, which can lead to memory leaks. When two or more objects reference each other, the use of lazy properties can prevent the need for one object to be fully initialized before the other.
  • Complex Initialization: For properties that require complex or resource-intensive initialization, lazy loading can be more efficient, particularly if the property is rarely used.

Declaring Lazy Properties

In Swift, you declare a lazy property using the lazy keyword. Here’s a basic example:

class ExampleClass {
    lazy var expensiveOperationResult: Int = {
        // Perform a complex and resource-intensive operation
        return 42

In this example, the expensiveOperationResult property is initialized lazily when it’s first accessed. The closure is executed only once when the property is first accessed, and the result is stored for future accesses.

Use Cases

Lazy properties are especially helpful in various scenarios, including:

  • Database Operations: When working with databases, you might not want to establish a connection until you need to access data.
  • View Controller Properties: Properties related to views in iOS apps can be initialized lazily to improve the app’s launch performance.
  • Resource-Intensive Calculations: For properties that require resource-intensive calculations, such as image processing or data parsing, you can use lazy properties to avoid unnecessary work.

By incorporating lazy properties into your Swift code, you can enhance the performance and efficiency of your applications while maintaining clean and readable code.

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