diff options
Diffstat (limited to 'src/doc/book/listings/ch15-smart-pointers/listing-15-23/src/lib.rs')
-rw-r--r-- | src/doc/book/listings/ch15-smart-pointers/listing-15-23/src/lib.rs | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-23/src/lib.rs b/src/doc/book/listings/ch15-smart-pointers/listing-15-23/src/lib.rs new file mode 100644 index 000000000..7d288e680 --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-23/src/lib.rs @@ -0,0 +1,78 @@ +pub trait Messenger { + fn send(&self, msg: &str); +} + +pub struct LimitTracker<'a, T: Messenger> { + messenger: &'a T, + value: usize, + max: usize, +} + +impl<'a, T> LimitTracker<'a, T> +where + T: Messenger, +{ + pub fn new(messenger: &'a T, max: usize) -> LimitTracker<'a, T> { + LimitTracker { + messenger, + value: 0, + max, + } + } + + pub fn set_value(&mut self, value: usize) { + self.value = value; + + let percentage_of_max = self.value as f64 / self.max as f64; + + if percentage_of_max >= 1.0 { + self.messenger.send("Error: You are over your quota!"); + } else if percentage_of_max >= 0.9 { + self.messenger + .send("Urgent warning: You've used up over 90% of your quota!"); + } else if percentage_of_max >= 0.75 { + self.messenger + .send("Warning: You've used up over 75% of your quota!"); + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + use std::cell::RefCell; + + struct MockMessenger { + sent_messages: RefCell<Vec<String>>, + } + + impl MockMessenger { + fn new() -> MockMessenger { + MockMessenger { + sent_messages: RefCell::new(vec![]), + } + } + } + + // ANCHOR: here + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + let mut one_borrow = self.sent_messages.borrow_mut(); + let mut two_borrow = self.sent_messages.borrow_mut(); + + one_borrow.push(String::from(message)); + two_borrow.push(String::from(message)); + } + } + // ANCHOR_END: here + + #[test] + fn it_sends_an_over_75_percent_warning_message() { + let mock_messenger = MockMessenger::new(); + let mut limit_tracker = LimitTracker::new(&mock_messenger, 100); + + limit_tracker.set_value(80); + + assert_eq!(mock_messenger.sent_messages.borrow().len(), 1); + } +} |