X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/4f61be32dd480f23a7fef05ee66c42ae27c980c6..74a318b63dab5abd344f17bf71932f87f8e349ab:/src/part03.rs?ds=sidebyside diff --git a/src/part03.rs b/src/part03.rs index 4a69aab..d8d71b1 100644 --- a/src/part03.rs +++ b/src/part03.rs @@ -33,8 +33,8 @@ fn read_vec() -> Vec { //@ details.) for line in stdin.lock().lines() { // Rust's type for (dynamic, growable) strings is `String`. However, our variable `line` - // here is not yet of that type: It rather has type `io::Result`. - //@ The problem with I/O is that it can always go wrong. The type of `line`is a lot like `Option` ("a `String` or + // here is not yet of that type: It has type `io::Result`. + //@ The problem with I/O is that it can always go wrong. The type of `line` is a lot like `Option` ("a `String` or //@ nothing"), but in the case of "nothing", there is additional information about the error. //@ Again, I recommend to check [the documentation](http://doc.rust-lang.org/stable/std/io/type.Result.html). //@ You will see that `io::Result` is actually just an alias for `Result`, so click on that to obtain @@ -50,12 +50,13 @@ fn read_vec() -> Vec { // access the "old" `line` again. let line = line.unwrap(); // Now that we have our `String`, we want to make it an `i32`. + //@ We first `trim()` the `line` to remove leading and trailing whitespace. //@ `parse` is a method on `String` that can convert a string to anything. Try finding it's documentation! //@ In this case, Rust *could* figure out automatically that we need an `i32` (because of the return type //@ of the function), but that's a bit too much magic for my taste. We are being more explicit here: //@ `parse::` is `parse` with its generic type set to `i32`. - match line.parse::() { + match line.trim().parse::() { //@ `parse` returns again a `Result`, and this time we use a `match` to handle errors (like, the user entering //@ something that is not a number). //@ This is a common pattern in Rust: Operations that could go wrong will return `Option` or `Result`.