Block passing is a feature in Rust 1.55 that allows one to pass a block of code as an argument to a function. This can be useful when you want to pass a block of code that needs to be executed later. It is syntax sugar for closures.
Here's an example:
fn main() {
let res = print_message(|| {
println!("Hello, world!");
});
}
fn print_message R, R>(f: F) -> R {
f()
}
In this example, we define a function called print_message that takes a closure as an argument. The || syntax is used to define a closure with no arguments. We then pass this closure as an argument to the print_message function.
When print_message is called, it executes the closure and returns its result. In this case, the closure simply prints a message to the console.
Block passing is also useful when working with asynchronous code. Here's an example:
async fn do_something R, R>(f: F) -> R {
f()
}
async fn main() {
let res = do_something(|| {
async {
// Perform some asynchronous operation here
}
}).await;
}
In this example, we define an async function called do_something that takes a closure as an argument. The closure contains an async block that performs some asynchronous operation.
When do_something is called, it executes the closure and returns its result. We then await the result in main.
In summary, block passing is a useful feature in Rust 1.55 that allows one to pass a block of code as an argument to a function. It can be used for both synchronous and asynchronous code and is helpful in cases where you need to execute a block of code later.