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Generic Types, Traits, and Lifetimes Every programming language has tools for effectively handling the duplication of concepts. In Rust, one such tool is generics: abstract stand-ins for concrete types or other properties. We can express th...
Generic Data Types We use generics to create definitions for items like function signatures or structs, which we can then use with many different concrete data types. Let’s first look at how to define functions, structs, enums, and methods...
Defining Shared Behavior with Traits A trait defines the functionality a particular type has and can share with other types. We can use traits to define shared behavior in an abstract way. We can use trait bounds to specify that a generic t...
Validating References with Lifetimes Lifetimes are another kind of generic that we’ve already been using. Rather than ensuring that a type has the behavior we want, lifetimes ensure that references are valid as long as we need them to be. O...
Writing Automated Tests In his 1972 essay “The Humble Programmer,” Edsger W. Dijkstra said that “program testing can be a very effective way to show the presence of bugs, but it is hopelessly inadequate for showing their absence.” That does...
How to Write Tests Tests are Rust functions that verify that the non-test code is functioning in the expected manner. The bodies of test functions typically perform these three actions: • Set up any needed data or state. • Run the code you...
Controlling How Tests Are Run Just as cargo run compiles your code and then runs the resultant binary, cargo test compiles your code in test mode and runs the resultant test binary. The default behavior of the binary produced by cargo test...
Test Organization As mentioned at the start of the chapter, testing is a complex discipline, and different people use different terminology and organization. The Rust community thinks about tests in terms of two main categories: unit tests...
An I/O Project: Building a Command Line Program This chapter is a recap of the many skills you’ve learned so far and an exploration of a few more standard library features. We’ll build a command line tool that interacts with file and comman...
Accepting Command Line Arguments Let’s create a new project with, as always, cargo new. We’ll call our project minigrep to distinguish it from the grep tool that you might already have on your system: $ cargo new minigrep Created binary (ap...
Reading a File Now we’ll add functionality to read the file specified in the file_path argument. First, we need a sample file to test it with: We’ll use a file with a small amount of text over multiple lines with some repeated words. Listin...
Refactoring to Improve Modularity and Error Handling To improve our program, we’ll fix four problems that have to do with the program’s structure and how it’s handling potential errors. First, our main function now performs two tasks: It pa...
Adding Functionality with Test-Driven Development Now that we have the search logic in src/lib.rs separate from the main function, it’s much easier to write tests for the core functionality of our code. We can call functions directly with v...
Working with Environment Variables We’ll improve the minigrep binary by adding an extra feature: an option for case-insensitive searching that the user can turn on via an environment variable. We could make this feature a command line optio...
Redirecting Errors to Standard Error At the moment, we’re writing all of our output to the terminal using the println! macro. In most terminals, there are two kinds of output: standard output (stdout) for general information and standard er...
Functional Language Features: Iterators and Closures Rust’s design has taken inspiration from many existing languages and techniques, and one significant influence is functional programming. Programming in a functional style often includes...
Closures Rust’s closures are anonymous functions you can save in a variable or pass as arguments to other functions. You can create the closure in one place and then call the closure elsewhere to evaluate it in a different context. Unlike f...
Processing a Series of Items with Iterators The iterator pattern allows you to perform some task on a sequence of items in turn. An iterator is responsible for the logic of iterating over each item and determining when the sequence has fini...
Improving Our I/O Project With this new knowledge about iterators, we can improve the I/O project in Chapter 12 by using iterators to make places in the code clearer and more concise. Let’s look at how iterators can improve our implementati...
Performance in Loops vs. Iterators To determine whether to use loops or iterators, you need to know which implementation is faster: the version of the search function with an explicit for loop or the version with iterators. We ran a benchma...
"Sometimes bad designs will fail faster in Rust"