mirror of https://github.com/rust-lang/book
79 lines
1.8 KiB
Rust
79 lines
1.8 KiB
Rust
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: &T, max: usize) -> LimitTracker<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
|