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contains and replace

Search with contains and replace with replace.

contains and replace

Methods for searching and replacing in text:

let m = "kedi ve kedi yavrusu";
m.contains("ve")            // true
m.starts_with("kedi")       // true
m.ends_with("su")           // true
m.find("yavru")             // Some(13): byte position
m.replace("kedi", "köpek")  // a new String
m.replacen("kedi", "at", 1) // only the first: "at ve kedi yavrusu"

replace returns a new String; the original text doesn't change.

Char and closure patterns

These methods accept not only text but also a char or a closure:

let s = "a1b2c3";
println!("{}", s.contains(char::is_numeric));       // true
println!("{:?}", s.find(|c: char| c.is_ascii_digit()));   // Some(1)
println!("{}", s.replace(|c: char| c.is_numeric(), "")); // abc
println!("{}", "--x--".trim_matches('-'));          // x

Practice Search and replace

For let metin = "kedi ve kedi yavrusu";, print the results of contains("ve"), find("yavru") ({:?}) and replace("kedi", "köpek") on one line separated by spaces.

Starter code

main.rs
fn main() {
    // buraya yaz
}

Sample solution

main.rs
fn main() {
    let metin = "kedi ve kedi yavrusu";
    println!("{} {:?} {}", metin.contains("ve"), metin.find("yavru"), metin.replace("kedi", "köpek"));
}

Expected output

true Some(13) köpek ve köpek yavrusu

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is <code>"Rust".contains("rust")</code>?

  • Compile error
  • false Correct answer
  • true
  • Some(0)

Explanation: Searching is case-sensitive. For a case-insensitive search, convert both sides with to_lowercase().

2 Replace all

Question 
let m = "kedi ve kedi";
let y = m.____("kedi", "at");   // "at ve at"
Answer 
let m = "kedi ve kedi";
let y = m.replace("kedi", "at");   // "at ve at"

Explanation: replace changes every match; replacen only the first n.

3 Expression and result on "kedi ve kedi"

Term Meaning
contains("ve") true
find("ve") Some(5)
replacen("kedi", "at", 1) "at ve kedi"
starts_with("ve") false

All lessons in Beginner

1 Rust basics

  1. What is Rust?
  2. Project with Cargo
  3. Your first program
  4. println! and formatting
  5. Comments
  6. Summary - Rust basics

2 Variables

  1. Variables with let
  2. Mutability with mut
  3. Constants with const
  4. Static variables
  5. Shadowing
  6. Summary - Variables

3 Data types

  1. Integers
  2. Floating point
  3. Bool and char
  4. Tuple
  5. Array
  6. Summary - Data types

4 Strings

  1. &str vs String
  2. Creating a String
  3. Concatenating strings
  4. format! macro
  5. String length
  6. Summary - Strings

5 Project: Calculator

  1. Project skeleton
  2. Reading input
  3. Computing
  4. Error handling
  5. Loop and exit

6 Functions

  1. Defining with fn
  2. Parameters
  3. Return value
  4. Expressions and statements
  5. Early return
  6. Summary - Functions

7 Control flow

  1. if-else
  2. match basics
  3. loop
  4. while loop
  5. for loop
  6. Summary - Control flow

8 Ownership

  1. What is ownership?
  2. Move semantics
  3. Copy trait
  4. Functions and ownership
  5. Return and ownership
  6. Summary - Ownership

9 Borrowing

  1. References
  2. Mutable reference
  3. Borrowing rules
  4. Dangling reference
  5. References and functions
  6. Summary - Borrowing

10 Slices

  1. String slices
  2. Slice syntax
  3. Array slices
  4. Slices and functions
  5. Range types
  6. Summary - Slices

11 Project: Guessing game

  1. Game skeleton
  2. Reading input
  3. Comparing numbers
  4. Random number
  5. Loop and exit

12 Structs

  1. Struct definition
  2. Creating an instance
  3. Tuple struct
  4. Unit-like struct
  5. Field update
  6. Summary - Structs

13 Methods

  1. impl block
  2. self parameter
  3. &mut self
  4. Associated functions
  5. Multiple impl blocks
  6. Summary - Methods

14 Enums

  1. Enum definition
  2. Variants
  3. Variants with data
  4. Option<T>
  5. Option instead of null
  6. Summary - Enums

15 Pattern matching

  1. match patterns
  2. Value binding
  3. if let
  4. while let
  5. _ wildcard
  6. Summary - Pattern matching

16 Project: To-do CLI

  1. Task model
  2. Adding
  3. Listing
  4. Marking done
  5. Reading commands

17 Vectors

  1. Vec<T>
  2. Push and pop
  3. Index and get
  4. Looping a vector
  5. with_capacity
  6. Summary - Vectors

18 Advanced strings

  1. String and &str conversion
  2. chars and bytes
  3. Slicing strings
  4. contains and replace
  5. split and join
  6. Summary - Advanced strings

19 Error handling

  1. Result<T, E>
  2. panic!
  3. ? operator
  4. match and Result
  5. unwrap and expect
  6. Summary - Error handling

20 Beginner final

  1. Vowel counter
  2. Average calculator
  3. Bank account
  4. Temperature converter