Any Trait

Runtime type introspection

Any Trait Basics

use std::any::Any;

fn main() {
    // Any allows runtime type checking
    let values: Vec<Box<dyn Any>> = vec![
        Box::new(42i32),
        Box::new("hello".to_string()),
        Box::new(3.14f64),
        Box::new(true),
    ];

    println!("=== Type Checking at Runtime ===");

    for (i, value) in values.iter().enumerate() {
        print!("Value {}: ", i);

        // is<T>() checks type
        if value.is::<i32>() {
            println!("is i32");
        } else if value.is::<String>() {
            println!("is String");
        } else if value.is::<f64>() {
            println!("is f64");
        } else if value.is::<bool>() {
            println!("is bool");
        }
    }

    // type_id() returns TypeId
    let value: Box<dyn Any> = Box::new(42);
    println!("\nTypeId: {:?}", value.type_id());
}