Module :: clone_dyn

Derive to clone dyn structures.

This crate is a facade that re-exports clone_dyn_types (for core traits and logic) and clone_dyn_meta (for procedural macros). It provides a convenient way to enable cloning for trait objects. By default, Rust does not support cloning for trait objects due to the Clone trait requiring compile-time knowledge of the type's size. The clone_dyn crate addresses this limitation through its procedural macros, allowing for cloning collections of trait objects. The crate's purpose is straightforward: it allows for easy cloning of dyn< Trait > with minimal effort and complexity, accomplished by applying the #[clone_dyn] attribute to the trait.

Alternative

There are few alternatives dyn-clone, dyn-clonable. Unlike other options, this solution is more concise and demands less effort to use, all without compromising the quality of the outcome.

Basic use-case

This example demonstrates the usage of the #[clone_dyn] attribute macro to enable cloning for trait objects.

#[ cfg( feature = "derive_clone_dyn" ) ]
#[ clone_dyn_meta::clone_dyn ] // Use fully qualified path
pub trait Trait1
{
  fn f1( &self );
}

#[ cfg( not( feature = "derive_clone_dyn" ) ) ]
pub trait Trait1
{
  fn f1( &self );
}

impl Trait1 for i32
{
  fn f1( &self ) {}
}

#[ cfg( feature = "derive_clone_dyn" ) ]
{
  let obj1: Box<dyn Trait1> = Box::new(10i32);
  let cloned_obj1 = obj1.clone(); // This should now work due to #[clone_dyn]
  // Example assertion, assuming f1() can be compared or has side effects
  // For a real test, you'd need a way to compare trait objects or their behavior.
  // For simplicity in doctest, we'll just ensure it compiles and clones.
  // assert_eq!(cloned_obj1.f1(), obj1.f1()); // This would require more complex setup
}
#[ cfg( not( feature = "derive_clone_dyn" ) ) ]
{
  // Provide a fallback or skip the example if macro is not available
}

When using clone_dyn with multithreaded or asynchronous code, the #[clone_dyn] macro automatically generates Clone implementations for all four trait object variants:

• Box<dyn Trait>
• Box<dyn Trait + Send>
• Box<dyn Trait + Sync>
• Box<dyn Trait + Send + Sync>

For a complete working example demonstrating this pattern with iterators, see examples/clone_dyn_trivial.rs.

Try out cargo run --example clone_dyn_trivial. See code.

To add to your project

cargo add clone_dyn

Try out from the repository

git clone https://github.com/Wandalen/wTools
cd wTools
cd examples/clone_dyn_trivial
cargo run