pub trait FilterMapFn<I, T, U>: Send + 'static {
// Required method
fn execute(&self, id: &I, data: T) -> Result<Option<U>>;
}Expand description
Filter map function.
This trait defines a function that transforms data of type T into optional
data of type U. It’s fundamentally the combination of the MapFn and
FilterFn traits, as it allows for filtering and mapping data as part
of a single operation. Since transformations can be expensive, this trait
expects owned data, so that operators are able to move the function into a
Task for execution on a worker thread.
There’s a range of different implementations of this trait, allowing you to
use a variety of function shapes, including support for Splat, as well
as support for the [WithId] and [WithSplat] adapters. Furthermore, the
trait can be implemented for custom types to add new behaviors. Note that
all implementations also allow to return a Report, which makes it
possible to return diagnostics from the function execution.
The 'static lifetimes is mandatory as closures must be moved into actions,
so requiring it here allows us to reduce the verbosity of trait bounds.
§Examples
Transform and filter data:
use zrx_stream::function::FilterMapFn;
// Define and execute function
let f = |n: i32| (n > 0).then(|| n * n);
f.execute(&"id", 42)?;Transform and filter data with splat argument:
use zrx_stream::function::{FilterMapFn, Splat};
// Define and execute function
let f = |a: i32, b: i32| (a < b).then(|| a + b);
f.execute(&"id", Splat::from((1, 2)))?;