diff options
Diffstat (limited to 'src/doc/book/listings/ch15-smart-pointers/listing-15-21')
4 files changed, 99 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-21/Cargo.lock b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/Cargo.lock new file mode 100644 index 000000000..4dc2226a5 --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/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-15-21/Cargo.toml b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/Cargo.toml new file mode 100644 index 000000000..98c3f537c --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/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-15-21/output.txt b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/output.txt new file mode 100644 index 000000000..6b07b66ea --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/output.txt @@ -0,0 +1,14 @@ +$ cargo test + Compiling limit-tracker v0.1.0 (file:///projects/limit-tracker) +error[E0596]: cannot borrow `self.sent_messages` as mutable, as it is behind a `&` reference + --> src/lib.rs:58:13 + | +2 | fn send(&self, msg: &str); + | ----- help: consider changing that to be a mutable reference: `&mut self` +... +58 | self.sent_messages.push(String::from(message)); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable + +For more information about this error, try `rustc --explain E0596`. +error: could not compile `limit-tracker` due to previous error +warning: build failed, waiting for other jobs to finish... diff --git a/src/doc/book/listings/ch15-smart-pointers/listing-15-21/src/lib.rs b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/src/lib.rs new file mode 100644 index 000000000..4572d4313 --- /dev/null +++ b/src/doc/book/listings/ch15-smart-pointers/listing-15-21/src/lib.rs @@ -0,0 +1,73 @@ +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::*; + + struct MockMessenger { + sent_messages: Vec<String>, + } + + impl MockMessenger { + fn new() -> MockMessenger { + MockMessenger { + sent_messages: vec![], + } + } + } + + impl Messenger for MockMessenger { + fn send(&self, message: &str) { + self.sent_messages.push(String::from(message)); + } + } + + #[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.len(), 1); + } +} +// ANCHOR_END: here |