- file_io2: replace the manual line_number counter with
.lines().enumerate(), and replace
buffered_file_writer.write(format!(...).as_bytes()) with writeln!,
which both formats and guarantees a complete write (write_fmt loops
internally, unlike a single Write::write call).
- file_io3: replace the manual match on file_path.parent() with
.ok_or_else(...)? for a more idiomatic Option-to-Result conversion.
Verified locally: both solutions compile under edition 2024, clippy is
silent, and running them still produces identical output (3 lines
processed / 117-byte file, non-readonly permissions) with no leftover
files.
dev-check runs clippy with -D warnings against the solutions, which
flagged the nested if let Some(dir_path) = ... { if dir_path.exists() ... }
in file_cleanup as collapsible. Combined into a single if-let with a
let-chain condition (edition = "2024", so this is available).
Verified locally: compiles under --edition 2024, clippy is silent,
and the binary still runs cleanly with file size 117 and no leftover
files.
- file_io3: replace the hardcoded expected file size (117) with
SAMPLE_TEXT.len(), so the check is derived from the actual content
instead of an unexplained magic number.
- file_io3: use create_dir_all instead of create_dir, and add a
sample_file_path() helper shared by main/create_required_files/
file_cleanup to avoid three separate ad-hoc path constructions.
- file_io1/file_io2: hoist the sample text into a SAMPLE_TEXT constant
used by both the exercise and its solution, removing duplicated
literals.
No behavioral change: all three solutions were rebuilt and run
locally, producing identical output (file size still 117, permissions
still non-readonly) with no leftover files.
Adds file_io1-3 (and their solutions) to dev/Cargo.toml's bin list so
'cargo dev check'/'cargo dev update' pick them up, and registers them in
rustlings-macros/info.toml with hints that explain each exercise's
learning goal and point at the relevant std API.
Adds three new exercises under exercises/24_file_io/, as proposed in rust-lang/rustlings#2233:
- file_io1: read a whole file with fs::read_to_string and handle the Result.
- file_io2: read/write a file efficiently with BufReader/BufWriter.
- file_io3: build a path with PathBuf and inspect it with .metadata().
Includes matching solutions and a README describing the learning goal of
each exercise.
To understand From-based conversion, an understanding of traits is
required, which we teach in a later chapter. The From trait specifically
is taught in one of the conversion exercises. So, we can safely remove
it here without users missing out on learning something important.
A specific source of confusion for users was a warning that the
conversion is useless, which appeared when using the `string_slice`
function for the expression with `.into()`. closes#2190
Conversion between Celsius and Fahrenheit should be understandable to
most. Inverting the formula is still not very hard, but a little harder
than only multiplying by 100.
Learners were sometimes confused by the literal array. Their assumption
was that they are supposed to convert the array to a vector. Duplicating
the literal elements was not an intuitive solution.
This redesign avoids putting an identical array literal near the place
where learners are supposed to use the vec! macro.
