dorfsmay / sorting-fruits-kata

A progressive kata to review Rust concepts by building a small apps step by step.

Picking up Rust

Material for picking up Rust for experienced developers:

Material from the RustBridge organisation:
https://intro.rustbridge.com/en/intro/#1

Rustlings: lots of TDD style exercises to practice Rust
https://github.com/rust-lang/rustlings

The sorting fruits kata

A progressive kata to review Rust concepts by building a small apps step by step.

Given one fruit name (or fruit type) per line in the files in the assets folder, concatenate them in a single file, "fruits.txt", ordered alphabetically. The full list is very small, therefore it can be kept and manipulated in memory before writing it out to file.

Before using this repository, make sure you run cargo init .

Reference

https://en.wikipedia.org/wiki/Fruit https://github.com/dorfsmay/sorting-fruits-kata

Steps

001 Print list of files

Learnings

• printing debug information {:?}
  https://doc.rust-lang.org/std/fmt/trait.Debug.html
• Introduction to Result and unwrap
  https://doc.rust-lang.org/stable/rust-by-example/error/option_unwrap.html
• for in loops
  https://doc.rust-lang.org/1.2.0/book/for-loops.html

Instructions

• create a function that:
  • take a String argument
  • print the list of files from the directory name given as the argument
• unwrap everything for now
• the function just prints, it does not return anything
• In the main function, create a String variable containing "assets"
• Use this variable to call your function

002 Result

Learnings

• Rust Result
  https://doc.rust-lang.org/std/result/ https://doc.rust-lang.org/std/fs/fn.read_dir.html
• ?. https://doc.rust-lang.org/edition-guide/rust-2018/error-handling-and-panics/the-question-mark-operator-for-easier-error-handling.html

Instructions

• Remove "unwrap"

003 Ownership

Learnings

• ownership: move, copy
• passing by reference / borrowing
• automatic dereferencing
• str vs String and string literals
  https://stackoverflow.com/questions/24158114/what-are-the-differences-between-rusts-string-and-str

Instructions

• Make your main print "Files inside folder folder-name before calling the function
• Note 1: You can create a reference to string literal, no need to convert to String
• Note 2: note how you do not need to change the type of the variable for read_dir (automatic dereferencing)

004 Print from the array

Learnings

• Rust Vectors and vec! macro
• mutable variables
• Rust guarding against non-initialised variables

Instructions

• Make the function return a Vector of PathBuff
• Keep using a loop to create the vector, don't jump into a turbo fish yet
• Make main to print them

005 Return an Option

Learnings

• Rust Option
  https://doc.rust-lang.org/std/option/
• if let

Instructions

• Add unit tests checkink for Some
• decide if you want to user unwrap for the unit tests, or make tem return a Result
• Make the function returning an Option
• adjust main

006 Vector manipulation

Learnings

• more ways to use modules
• crate prelude
  https://stackoverflow.com/questions/36384840/what-is-the-prelude

Instructions

• Add a function to read the content of a file into a vector
• make main concatenate the content of all the files into a single vector
• make main sort the list of words (using the Vector sort)
• make main print the entire list