# Objective
In the past I had custom data structures containing `Tick`s. I learned
that these need to be regularly checked to clamp them. But there was no
way to hook into that logic so I abandoned storing ticks since then.
Another motivation to open this up some more is to be more able to do a
correct implementation of `System::check_ticks`.
## Solution
Add `CheckChangeTicks` and trigger it in `World::check_change_ticks`.
Make `Tick::check_tick` public.
This event makes it possible to store ticks in components or resources
and have them checked.
I also made `Schedules::check_change_ticks` public so users can store
schedules in custom resources/components for whatever reasons.
## Testing
The logic boils down to a single `World::trigger` call and I don't think
this needs more tests.
## Alternatives
Making this obsolete like with #15683.
---
## Showcase
From the added docs:
```rs
use bevy_ecs::prelude::*;
use bevy_ecs::component::CheckChangeTicks;
#[derive(Resource)]
struct CustomSchedule(Schedule);
let mut world = World::new();
world.add_observer(|tick: Trigger<CheckChangeTicks>, mut schedule: ResMut<CustomSchedule>| {
schedule.0.check_change_ticks(tick.get());
});
```
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Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
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