When we write a real-world application, the Rust language and its standard library are not sufficient. Application frameworks are needed for particular kinds of applications, such as GUI apps, web apps, or games.
Of course, if you use a good-quality and comprehensive library, you can reduce the number of lines of code that you need to write. Using a library also offers the following two advantages:
- The overall design is improved, particularly if you are using a framework (since it imposes an architecture on your app) as it will be created by knowledgeable engineers and time-tested by a number of users.
- The number of bugs will be reduced because it will have undergone more thorough testing than that which you are likely to be able to apply.
There are actually many Rust libraries, also known as crates, but most are low-quality or quite narrow in their range of applications. This book will look at the best quality and most complete libraries for some typical application areas of the Rust language.
The application areas are as follows:
- Web apps: There are various popular technologies, including the following:
- The REST web service (backend only)
- An event-driven web client (frontend only)
- A full web app (full-stack)
- A web game (frontend only)
- Games: When I say games, I'm not referring to anything that is entertaining. I am referring to a graphical application where a continuous animation is shown, as opposed to event-driven graphical applications that do nothing until an event occurs, such as the user pressing a key, moving the mouse, or some data arriving from a connection. As well as games for the web browser, there are also games for desktop and laptop computers, for video game consoles, and for mobile devices. However, video game consoles and mobile devices are not yet that well supported by Rust, so we will only be looking at games for desktop and laptop computers in this book.
- Language interpreters: There are two kinds of languages that can be interpreted. Both are covered in this book:
- Text: Like a programming language, a markup language, or a machine command language
- Binary: Like the machine language of a computer to be emulated, or the intermediate bytecode of a programming language.
- C-language-callable libraries: This is an important use case of Rust: to develop a library to be invoked by another application, typically written in a higher-level language. Rust cannot assume that other languages can invoke the Rust code, but it can assume that they can invoke the C-language code. We will look at how to build a library that can be invoked as if it were written in C. One particularly challenging case is to build a module for the Linux operating system, which notoriously has to be written in C.
Most applications read and write data to and from a file, or a communication channel, or a database. In the next chapter, we will be looking at various different techniques that will be useful for all the other projects.
Other application areas have not been listed here as they are either not used much in Rust, they are still immature, or they are still in a state of flux. The libraries available for these immature areas will be completely different in a couple of years. These areas include software for micro-controllers, or other real-time or low-resource systems, and also software for mobile or wearable systems.