If let some match…

In Rust, you can use the if let expression to conditionally match and destructure an enum variant or a pattern and execute code based on whether the match is successful or not.

Example 1

enum SomeEnum {
    SomeName(String),
    NoneValue,
}

fn main() {
    // Create a vector of 'SomeEnum' instances with names
    let names = vec![
        SomeEnum::SomeName("Alice".to_string()),
        SomeEnum::NoneValue,
        SomeEnum::SomeName("Bob".to_string()),
        SomeEnum::SomeName("Moo".to_string()),
        SomeEnum::NoneValue,
        SomeEnum::NoneValue,
    ];

    for name in names {
        // Use 'if let' to check if 'name' is a 'SomeName' variant and extract the name
        if let SomeEnum::SomeName(inner_name) = name {
            // Use 'match' to further process the extracted name
            match inner_name.as_str() {
                "Alice" => println!("Found a SomeName variant with name Alice"),
                "Bob" => println!("Found a SomeName variant with name Bob"),
                _ => println!("Found a SomeName variant with an unknown name"),
            }
        } else {
            println!("Did not find a SomeName variant.");
        }
    }
}

Example 2

enum ProductStatus {
    InStock,
    OutOfStock,
}

struct Product {
    name: String,
    price: f64,
    status: ProductStatus,
}

fn main() {
    // Create a list of products
    let products = vec![
        Product {
            name: "Smartphone".to_string(),
            price: 599.99,
            status: ProductStatus::InStock,
        },
        Product {
            name: "Laptop".to_string(),
            price: 999.99,
            status: ProductStatus::InStock,
        },
        Product {
            name: "Tablet".to_string(),
            price: 299.99,
            status: ProductStatus::OutOfStock,
        },
    ];

    // Display the products and their availability
    println!("Product Inventory:");

    for product in &products {
        if let ProductStatus::InStock = product.status {
            match product.name.as_str() {
                "Smartphone" => {
                    println!("Special Offer: {} - Price: ${:.2} - In Stock", product.name, product.price);
                },
                _ => {
                    println!("Product: {} - Price: ${:.2} - In Stock", product.name, product.price);
                }
            }
        } else {
            println!("Product: {} - Status: Out of Stock", product.name);
        }
    }
}