Rust, Software Development

Things You Need To Know About Strings When Learning Rust

99% of the time, we deal with strings, which are a sequence of characters, and here are the things you need to know about them when learning Rust.

1. There Are 2 Types of String in Rust: String and str

Rust has essentially two types of string – String and str. A String is a growable, mutable, owned, and UTF-8 encoded string type, while str, which is only accessible via &str type, is a pointer to a String somewhere in the stack, heap, or in binary (e.g., literal string values). Using str is the preferred way to pass a read-only string around.

If we used String instead of &str, we would get a compile-time error.

The actual compile-time error is as follows.

2. Ways You Can Create Rust Strings from str

One, we can create an empty string using String::new().

Second, we can convert a string literal to a String using to_string and from functions.

Note that other functions can convert str to String.

3. Rust Strings are UTF-8 encoded

Not all programming languages have UTF-8 encoded strings. Java strings, for instance, are UTF-16 encoded, while Rust strings are in UTF-8.

These codes output these:

4. Ways You Can Update Rust Strings

We can use the push_str function to append a string to an existing string.

Another related function, called a push, appends a character to a string.

5. Ways You Can Concatenate Rust Strings

When concatenating two strings, the second string must reference a string.

Why did we use &name_state? If we check out Rust file, we will see this:

Another way to concatenate strings is by using the format! macro.

6. Rust Does Not Support Indexing; use String Slicing Instead

First, the usual syntax found in other languages for string indexing does not work in Rust.

These codes will not compile.

Since strings are UTF-8 encoded and can contain non-English characters, consider these codes.

We would expect to see three characters, but internally Rust considers the string to be having a length of 9. As a result, Rust puts restrictions and disallows string indexing. To make the codes work, we need to use string slices.

If that is the case, how to loop through a String if we need to? We can use the chars() function.

The codes print out:

7. Compare Rust Strings using !=, ==, =>,  <=, <, and > operators

Strings in Rust implement the PartialEq trait.

You need to know these things about strings to make your learning of Rust easier.

Tested with Rust 1.40.0.


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