Chapter 9: Error Handling
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src/main.rs
42
src/main.rs
@ -10,6 +10,7 @@ fn main() {
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chapter_6();
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chapter_7();
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chapter_8();
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chapter_9();
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}
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fn chapter_1() {
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@ -996,3 +997,44 @@ fn hash_maps() {
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println!();
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}
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fn chapter_9() {
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unrecoverable_errors_with_panic();
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recoverable_errors_with_result();
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panic_or_result();
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println!();
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}
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fn unrecoverable_errors_with_panic() {
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println!("The `panic!` macro crash the program gracefully. We may configure it to abort instead.");
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println!("If we want the stacktrace we need to set the environment variable: `RUST_BACKTRACE`.");
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println!();
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}
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fn recoverable_errors_with_result() {
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println!("The `Result` enum enable a function to return a recoverable error.");
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println!("We may check for a kind of error by stacking the `match`.");
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println!("Instead we may prefer to use closures to better communicate our intention and not use to much nested `match`.");
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println!("For example `unwrap` and `expect` are shortcuts to panic on error.");
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println!("See chapter 13 for more infos.");
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println!("If we want to let the caller take care of the errors we encounter we can propagate the error with `?`");
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println!("Fun example (ending with a bit of a cheat): https://doc.rust-lang.org/stable/book/2018-edition/ch09-02-recoverable-errors-with-result.html#propagating-errors");
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println!();
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}
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fn panic_or_result() {
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println!("It is ok to panic! when in `Examples, Prototype Code, and Tests`");
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println!("For the examples and when prototypying `unwrap` and `expect` are clear markers showing where to handle the errors");
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println!("When testing panicking is the way to tell that the test failed");
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println!("When we hardcode a value (or have more infos than the compiler)");
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println!("We can also panic when the developper using our library break one of our contract.");
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println!("Each time we create contract like this we should document them.");
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// Example: Trying to access an array/Vec<> after a it's max length (out-of-bounds)
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println!();
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}
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