Tracker - track changes to structs efficiently
Tracker is a small crate that allows you to track changes to struct fields.
It implements the following methods for your struct fields:
-
get_#field_name()
Get a immutable reference to your field -
get_mut_#field_name()
Get a mutable reference to your field. Assumes the field will be modified and marks it as changed. -
set_#field_name(value)
Get a mutable reference to your field. Marks the field as changed only if the new value isn't equal with the previous value. -
update_#field_name(fn)
Update your mutable field with a function or closure. Assumes the field will be modified and marks it as changed.
To check for changes you can call var_name.changed(StructName::field_name())
and it will return a bool.
To reset all previous changes you can call var_name.reset()
.
How it works
Let's have a look at a small example.
What happens behind the scenes when you call set_x()
is that a bitflag is set in the tracker field of your struct:
y x
tracker: u8 = | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
set_x(42) -> | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
reset() -> | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
As you can see this works pretty efficient. The macro expansion looks like this:
Further attributes
You can mark fields as
do_not_track
if you don't want tracker to implement anything for this fieldno_eq
if the type of the field doesn't implement PartialEq or tracker should not check for equality when callingset_#field_name(value)
so that even overwriting with the same value marks the field as changed.