Crate type_census
source · [−]Expand description
Track the number of extant instances of your types.
Example
// 1. import these three items:
use type_census::{counter, Instance, Tabulate};
#[derive(Clone)]
pub struct Foo<T> {
v: T,
// 2. add a field of type `Instance<Self>`
_instance: Instance<Self>,
}
impl<T> Foo<T>
{
pub fn new(v: T) -> Self
where
// 3. add a `Self: Tabulate` bound to constructors
Self: Tabulate,
{
Self {
v,
// 4. and initialize your `Instance` field like so:
_instance: Instance::new(),
}
}
pub fn v(self) -> T {
self.v
}
}
// 5. finally, implement `Tabulate` like this:
impl<T> Tabulate for Foo<T> {
counter!();
}
fn main() {
// you can now query the number of extant instances of `Foo`!
assert_eq!(Foo::<i8>::instances(), 0);
assert_eq!(Foo::<u8>::instances(), 0);
// the same counter is shared for all generic instantiations
let mut bar: Vec<Foo<i8>> = vec![Foo::new(0i8); 10];
assert_eq!(Foo::<i8>::instances(), 10);
assert_eq!(Foo::<u8>::instances(), 10);
let _baz: Vec<Foo<u8>> = vec![Foo::new(0u8); 5];
assert_eq!(Foo::<i8>::instances(), 15);
assert_eq!(Foo::<u8>::instances(), 15);
let _ = bar.drain(0..5);
assert_eq!(Foo::<i8>::instances(), 10);
assert_eq!(Foo::<u8>::instances(), 10);
}
Macros
Generates a correct implementation of Tabulate::counter
.
Structs
A zero-sized guard that tracks the lifetime of an instance of T
.
Traits
Track the population of Self
.