Computed Properties in Rust: How to Implement Them Effectively

Computed Properties in Rust: How to Implement Them Effectively

Introduction

• Using Getter Methods (No Caching)
• Using Lazy Computation with OnceLock (Efficient Caching)
• Mutable Caching with RefCell
• Thread-Safe Caching with Mutex
• Optimized Reads with RwLock
• Comparison Table
• Final Thoughts

Computed properties dynamically calculate values when accessed instead of storing them. While languages like Swift and JavaScript support them natively, Rust requires explicit patterns. This guide covers five approaches to replicate computed properties in Rust, including thread-safe solutions for concurrent code.

In Swift, a computed property recalculates its value on access:

struct Rectangle {
    var width: Double
    var height: Double

    var area: Double { // Computed property
        width * height
    }
}

let rect = Rectangle(width: 10, height: 20)
print(rect.area) // 200s

Using Getter Methods (No Caching)

📌 Best for: Simple calculations or frequently changing values.

In Rust, the most straightforward way to emulate a “computed property” is to write a getter method that calculates the value on each call.

🦀 Rust Implementation

#[derive(Debug)]
struct Rectangle {
    width: f64,
    height: f64,
}

impl Rectangle {
    fn area(&self) -> f64 {
        self.width * self.height
    }
}

fn main() {
    let rect = Rectangle { width: 10.0, height: 20.0 };
    println!("Area: {}", rect.area()); // 200.0
}

Read the full blog post here:
https://minikin.me/blog/computed-properties-in-rust