Difference between revisions of "Rust-Programming-Language/C2/Strings/English"

Learning Objectives

• String data type

System Requirements

• To record this tutorial I’m using the following setup.

Code Files

stringsdemo.rs

• The following code file is required to practise this tutorial

• This file is provided in the code files link of this tutorial page

Strings

• String Literal(&str) i.e string slice and
• String Object(String)

String Literal

• A string literal is a statically allocated string stored in the program's binary
• It is written using double quotes (")
• String literals are also known as string slices.

String slice

• Eg: let name: &str = "Rust Program";

• A string slice is a reference to a part of a string.
• It's represented by the type &str
• A string slice cannot be modified as it points to a part of memory that holds the string.

> cargo new stringsdemo

In the menu bar, File >> Open folder >> Desktop >> MyRustProject >> stringsdemo

Type the command cargo new stringsdemo and press Enter.

Open the created project as shown.

fn main() {

let s = String::from("Hello, world!");

let x = &s[0..5]; // A slice of the first 5 characters

println!("{}", x); // output: Hello

}

String::from creates a new String object from a string literal ("Hello, world!").

Variable x takes a slice of the string s.

0 to 5 is a range that means "from index 0 up to index 5".

Note that the slicing excludes the end index character.

As x references part of s, it doesn’t own the String. So no new memory is allocated to it.

So, it gives you the substring "Hello".

Save the program.

In the menu bar, click on Terminal and select New Terminal.

In the terminal, type cargo run

We can see Hello is printed as the output.

String Objects

• String Object is mutable, growable and heap allocated string type.
• It is commonly used when the strings can be modified and dynamically sized.
• It automatically frees the memory when it goes out of scope.

Copy and paste the code from the code file for each function in the below demonstration.

let s = String::from("Hello World");

println!("Length: {}", s.len()); // Outputs: 11

}

> cargo run

The len() function returns the total number of characters in a string, including the spaces.

Save the program.

Run the program.

We can see the length of the string printed as 11.

let mut s = String::from("Hello");

s.clear();

println!("Cleared string: {}", s); // Outputs an empty line

}

The clear() function clears the string and returns an empty string.

Run the program.

We can see the empty string as output.

let s = String::from("I love Rust");

let new_s = s.replace("love", "enjoy");

println!("{}", new_s); }

// Outputs: I enjoy Rust

This program replaces all matches of a pattern with another string.

Let us run the program and verify the output.

We can see that the string “love” is replaced with “enjoy”.

let mut s = "Tutorial".to_string();

s.push('s');

println!("{}",s);

}

Push() function appends the given char to the end of this String.

Run the program .

In the output, “s” is added at the end of the string “tutorial”.

let s = String::from("Hello, Rust, World");

for item in s.split(", ") {

println!("{}", item);

}

}

It splits the string, whenever it encounters a comma and space.

It returns an iterator over substrings separated by that pattern.

The for loop consumes the iterator and prints each substring on a new line.

In the terminal, run the program and check the output.

We can see each string slice printed on a new line.

let str = String::from("Hello");

// Loop through each character in a string using chars() method

for char in str.chars() {

println!("{}", char);

}

}

We can use the chars() method of the string type to iterate over a string.

Let us check the output.

We can see each character of the string is printed in a separate line.

fn main() {

let fullname = " Spoken Tutorials \r\n";

println!("Before trim ");

println!("length is {}",fullname.len());

println!();

println!("After trim ");

println!("length is {}",fullname.trim().len());

}

The trim() function removes leading and trailing spaces in a string.

This will not remove the inline spaces.

Save the program.

Analyse the output.

Additional reading material

• Please go through the additional reading material provided in the link of this tutorial.

• You will learn more about string memory allocation concept and other string methods.

Summary

In this tutorial, we learnt about

• String data type

Let us summarize.

Assignment

fn main(){

let mut title = " Spoken Tutorial".to_string();

title.push_str(" Project");

println!("{}",title);

}

• Run the above code
• Understand the difference between push and push_str function.