For this chapter, we only need access to the internet as we will be using the online Rust playground to implement the code. The code examples provided can be run in the online Rust playground at https://play.rust-lang.org/.

For detailed instructions, please refer to the file found here: https://github.com/PacktPublishing/Rust-Web-Programming-2nd-Edition/tree/main/chapter01

With programming, there is usually a trade-off between speed and resources and development speed and safety. Low-level languages such as C/C++ can give the developer fine-grained control over the computer with fast code execution and minimal resource consumption. However, this is not free. Manual memory management can introduce bugs and security vulnerabilities. A simple example of this is a buffer overflow attack. This occurs when the programmer does not allocate enough memory. For instance, if the buffer only has a size of 15 bytes, and 20 bytes are sent, then the excess 5 bytes might be written past the boundary. An attacker can exploit this by passing in more bytes than the buffer can handle. This can potentially overwrite areas that hold executable code with their own code. There are other ways to exploit a program that does not have correctly managed memory. On top of increased vulnerabilities, it takes more code and time to solve a problem in a low...

If you have coded in another language before, you will have used variables and handled different data types. However, Rust does have some quirks that can put off developers. This is especially true if the developer has come from a dynamic language, as these quirks mainly revolve around memory management and reference to variables. These can be intimidating initially, but when you get to understand them, you will learn to appreciate them. Some people might hear about these quirks and wonder why they should bother with the language at all. This is understandable, but these quirks are why Rust is such a paradigm-shifting language. Working with borrow checking and wrestling with concepts such as lifetimes and references gives us the high-level memory safety of a dynamic language such as Python. However, we can also get memory safe low-level resources such as those delivered by C and C++. This means that we do not have to worry about dangling pointers...

As we remember from the beginning of the chapter, Rust does not have a garbage collector. However, it has memory safety. It achieves this by having strict rules around variable ownership. These rules are enforced when Rust is being compiled. If you are coming from a dynamic language, then this can initially lead to frustration. This is known as fighting the borrow checker. Sadly, this unjustly gives Rust the false steep learning curve reputation, as when you are fighting the borrow checker without knowing what is going on, it can seem like an impossible task to get even the most basic programs written. However, if we take the time to learn the rules before we try and code anything too complex, the knowledge of the rules and the helpfulness of the compiler will make writing code in Rust fun and rewarding. Again, I take the time to remind you that Rust has been the most favorited language 7 years in a row. This is not because it’s impossible to get...

In modern high-level dynamic languages, objects have been the bedrock for building big applications and solving complex problems, and for good reason. Objects enable us to encapsulate data, functionality, and behavior. In Rust, we do not have objects. However, we do have structs that can hold data in fields. We can then manage the functionality of these structs and group them together with traits. This is a powerful approach, and it gives us the benefits of objects without the high coupling, as highlighted in the following figure:

Figure 1.10 – Difference between Rust structs and objects

We will start with something basic by creating a Human struct with the following code:

#[derive(Debug)]
struct Human<'a> {
    name: &'a str,
    age: i8,
    current_thought: &'a str
}

In the preceding code, we can see that our string literal fields have...

Metaprogramming can generally be described as a way in which the program can manipulate itself based on certain instructions. Considering the strong typing Rust has, one of the simplest ways in which we can meta program is by using generics. A classic example of demonstrating generics is through coordinates, as follows:

struct Coordinate <T> {
    x: T,
    y: T
}
fn main() {
    let one = Coordinate{x: 50, y: 50};
    let two = Coordinate{x: 500, y: 500};
    let three = Coordinate{x: 5.6, y: 5.6};
}

In the preceding snippet, we can see that the Coordinate struct managed to take in and handle three different types of numbers. We can add even more variance to the Coordinate struct so we can have two different types of numbers in one struct with the following code:

struct Coordinate <T, X> {
    x: T,
   ...

With Rust, we have seen that there are some traps when coming from a dynamic programming language background. However, with a little bit of knowledge of referencing and basic memory management, we can avoid common pitfalls and write safe, performant code quickly that can handle errors. By utilizing structs and traits, we can build objects that are analogous to classes in standard dynamic programming languages. On top of this, the traits enabled us to build mixin-like functionality. This not only enables us to slot in functionality when it’s useful to us but also perform checks on the structs through typing to ensure that the container or function is processing structs with certain attributes belonging to the trait that we can utilize in the code.

With our fully functioning structs, we bolted on even more functionality with macros and looked under the hood of basic macros by building our own capitalize function, giving us guidance for further reading and debugging...

1. What is the difference between str and String?
2. Why can’t string slices be passed into a function (string slice meaning str as opposed to &str)?
3. How do we access the data belonging to a key in a HashMap?
4. When a function results in an error, can we handle other processes, or will the error crash the program instantly?
5. Why does Rust only allow one mutable borrow at a point in time?
6. When would we need to define two different lifetimes in a function?
7. How can structs link to the same struct via one of their fields?
8. How can we add extra functionality to a struct where the functionality can also be implemented by other structs?
9. How do we allow a container or function to accept different data structures?
10. What’s the quickest way to add a trait, such as Copy, to a struct?

1. String is a fixed-size reference stored in the stack that points to string-type data on the heap. str is an immutable sequence of bytes stored somewhere in memory. Because the size of str is unknown, it can only be handled by a &str pointer.
2. Since we do not know the size of the string slice at compile time, we cannot allocate the correct amount of memory for it. Strings, on the other hand, have a fixed-size reference stored on the stack that points to the string slice on the heap. Because we know this fixed size of the string reference, we can allocate the correct amount of memory and pass it through to a function.
3. We use the HashMap’s get function. However, we must remember that the get function merely returns an Option struct. If we are confident that there is something there or we want the program to crash if nothing is found, we can directly unwrap it. However, if we don’t want that, we can use a match statement and handle the Some and None...

• Hands-On Functional Programming in Rust (2018) by Andrew Johnson, Packt Publishing
• Mastering Rust (2019) by Rahul Sharma and Vesa Kaihlavirta, Packt Publishing
• The Rust Programming Language (2018): https://doc.rust-lang.org/stable/book/
• The Problem With Single-threaded Shared Mutability (2015) by Manish Goregaokar: https://manishearth.github.io/blog/2015/05/17/the-problem-with-shared-mutability/