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Alternatives to drain to preventable multiple mutable refs to self
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| use std::collections::VecDeque; | |
| #[derive(Debug, Clone)] | |
| struct Event(u32); | |
| struct Context { | |
| queued_events: VecDeque<Event>, | |
| } | |
| impl Context { | |
| fn new() -> Self { | |
| let mut queued_events = VecDeque::new(); | |
| queued_events.push_back(Event(1)); | |
| queued_events.push_back(Event(2)); | |
| queued_events.push_back(Event(3)); | |
| Context { queued_events } | |
| } | |
| fn process_event(&mut self, event: &Event) { | |
| println!(" Processing event: Event({})", event.0); | |
| self.some_other_method(); | |
| } | |
| fn some_other_method(&mut self) { | |
| println!(" Called some_other_method"); | |
| } | |
| fn process_events_drain(&mut self) { | |
| println!("1. Using drain() - This will not compile:"); | |
| // Uncommenting the next line will cause a compilation error | |
| // self.queued_events.drain(..).for_each(|event| self.process_event(&event)); | |
| // Error: cannot borrow `self` as mutable more than once at a time | |
| println!(" (Compilation error if uncommented)"); | |
| } | |
| fn process_events_clone(&mut self) { | |
| println!("\n2. Using clone (works but maybe inefficient):"); | |
| let events = self.queued_events.clone(); | |
| for event in &events { | |
| self.process_event(event); | |
| } | |
| self.queued_events.clear(); | |
| println!(" Queue size: {}", self.queued_events.len()); | |
| } | |
| fn process_events_pop_front(&mut self) { | |
| println!("\n3. Using while let with pop_front():"); | |
| while let Some(event) = self.queued_events.pop_front() { | |
| self.process_event(&event); | |
| } | |
| println!(" Queue size: {}", self.queued_events.len()); | |
| } | |
| fn process_events_take(&mut self) { | |
| println!("\n4. Using std::mem::take():"); | |
| let events = std::mem::take(&mut self.queued_events); | |
| for event in &events { | |
| self.process_event(event); | |
| } | |
| println!(" Queue size: {}", self.queued_events.len()); | |
| } | |
| fn process_events_replace(&mut self) { | |
| println!("\n5. Using std::mem::replace() with new():"); | |
| let events = std::mem::replace(&mut self.queued_events, VecDeque::new()); | |
| for event in &events { | |
| self.process_event(event); | |
| } | |
| println!( | |
| " Queue size after processing: {}", | |
| self.queued_events.len() | |
| ); | |
| } | |
| } | |
| fn main() { | |
| let mut context = Context::new(); | |
| context.process_events_drain(); | |
| context = Context::new(); | |
| context.process_events_clone(); | |
| context = Context::new(); | |
| context.process_events_pop_front(); | |
| context = Context::new(); | |
| context.process_events_take(); | |
| context = Context::new(); | |
| context.process_events_replace(); | |
| } |
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