diff options
Diffstat (limited to 'src/doc/book/listings/ch15-smart-pointers/listing-15-22')
3 files changed, 90 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.lock b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.lock new file mode 100644 index 000000000..4dc2226a5 --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.lock @@ -0,0 +1,6 @@ +# This file is automatically @generated by Cargo. +# It is not intended for manual editing. +[[package]] +name = "limit-tracker" +version = "0.1.0" + diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.toml b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.toml new file mode 100644 index 000000000..98c3f537c --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/Cargo.toml @@ -0,0 +1,6 @@ +[package] +name = "limit-tracker" +version = "0.1.0" +edition = "2021" + +[dependencies] diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-22/src/lib.rs b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/src/lib.rs new file mode 100644 index 000000000..a77ffa41c --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-22/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!"); + } + } +} + +// ANCHOR: here +#[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![]), + } + } + } + + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + self.sent_messages.borrow_mut().push(String::from(message)); + } + } + + #[test] + fn it_sends_an_over_75_percent_warning_message() { + // --snip-- + // ANCHOR_END: here + let mock_messenger = MockMessenger::new(); + let mut limit_tracker = LimitTracker::new(&mock_messenger, 100); + + limit_tracker.set_value(80); + // ANCHOR: here + + // ANCHOR: here + assert_eq!(mock_messenger.sent_messages.borrow().len(), 1); + } +} +// ANCHOR_END: here |