Useless lifetimes

[Bowarc]

Hellow, im tring to have some sort of dynamic Activity, But the fact that activity::Activity uses Option<&'a str> instead of Option<String> + that it's returning self for each function makes that it's rly hard to use imo. I made a config-like structure to be used in .ron files so i can add or remove parts easily (I know it's supposed to be chained but i can't find a way to make it work with the optional config that i am using) Example:

let mut activity = activity::Activity::new();
match activity_config.state {
    Some(state) => {
        debug!("Activity::State set to: {}", state);
        activity = activity.state(state);
    }
    None => debug!("Activity::State not found"),
}
match activity_config.details {
    Some(details) => {
        debug!("Activity::Details set to: {}", details);
        activity = activity.details(details);
    }
    None => debug!("Activity::Details not found"),
}

This is impossible with the current type of activity::Activity The example above is working if you replace every Option<&'a str> by Option<String> and remove lifetimes on activity::Activity

It might just be me as im not very experienced with lifetimes, but i see no advantage of using Option<&'a str> instead of Option<String>.

[antiaim]

Agreed, was trying to run the ipc client in a thread but couldnt share the Activity struct with the thread because of the lifetimes. ended up having to just make another struct that contains the data and sharing that instead.

[vionya]

First thing to disclose: it's been a hot minute since I implemented the Activity interface, so I unfortunately cannot tell you my original thought process behind the lifetimes and everything.

That aside, would it be preferable to make a breaking change wherein instead of chaining, it instead has set_* operations that modify it in-place?

let mut activity = Activity::new();
match activity_config.state {
    Some(state) => {
        debug!("Activity::State set to: {}", state);
        activity.set_state(state);
    }
    None => debug!("Activity::State not found"),
}
match activity_config.details {
    Some(details) => {
        debug!("Activity::Details set to: {}", details);
        activity.set_details(details);
    }
    None => debug!("Activity::Details not found"),
}

Thanks for the thread :)

[Bowarc]

Yes, why not. Having functions like

Activity::set_state(&mut self, new_state: &str) -> () {
    self.state=new_state
}

Could be very helpfull for thoses kind of scenarios.

[vionya]

Alright, I'll plan to replace the current system with something like that in the next major version.

[Bowarc]

I tried a bit more and it turns out that, in my case, using the kw ref in the Some() section of the match compiles.

match activity_config.state {
    Some(ref state) => {
        debug!("Activity::State set to: {}", state);
        activity = activity.state(&state);
    }
    None => debug!("Activity::State not found"),
}
match activity_config.details {
    Some(ref details) => {
        debug!("Activity::Details set to: {}", details);
        activity = activity.details(&details);
    }
    None => debug!("Activity::Details not found"),
}

Even if that case worked; for other scenarios, having functions that take &mut self would be greatly appreciated.