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Summary - Advanced strings

Combine split, RegExp and StringBuffer to write a CSV parser.

Summary - Advanced strings

In this group you saw four powerful string tools: split and join for string-list conversion, replaceAll for bulk replacement, trim and padLeft for formatting, RegExp for pattern search, StringBuffer for efficient building. Now we combine them all in a CSV parser.

A CSV line holds comma-separated fields. You split with split, clean spaces with trim, validate digits with RegExp and produce a new formatted output with StringBuffer. This is string tools working together on a real task.

Practice Your turn: parse a CSV line

Split the line "anna, 28 , paris" on the comma, clean each part with trim and join them with StringBuffer using "|" as the separator. Print the result.

Starter code

main.dart
void main() {
  // Split "anna, 28 , paris" on the comma
  // Trim each part
  // Join with StringBuffer and "|" then print
}

Sample solution

main.dart
void main() {
  final line = "anna, 28 , paris";
  final parts = line.split(",").map((s) => s.trim()).toList();
  final sb = StringBuffer();
  for (var i = 0; i < parts.length; i++) {
    if (i > 0) sb.write("|");
    sb.write(parts[i]);
  }
  print(sb.toString());
}

Expected output

anna|28|paris

Practice Your turn: validate and format fields

Split "book, 120 , 2024", trim each part. Check the third part with RegExp(r"\d{4}") using hasMatch and print the result.

Starter code

main.dart
void main() {
  // Split "book, 120 , 2024" and trim each part
  // Check the third part with a four-digit pattern
  // Print the result
}

Sample solution

main.dart
void main() {
  final line = "book, 120 , 2024";
  final parts = line.split(",").map((s) => s.trim()).toList();
  print(RegExp(r"\d{4}").hasMatch(parts[2]));
}

Expected output

true

Questions and answers

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

1 First step to extract fields from a CSV line?

main.dart
final line = "anna,28,paris";
final fields = line._____(",");
  • trim
  • split Correct answer
  • join
  • pad

Explanation: split turns the fields into a list.

2 Match the CSV tools

Term Meaning
split(",") splits the fields
trim() cuts spaces
RegExp(r"\d+") validates the age
StringBuffer builds the output

All lessons in Beginner

1 Dart basics

  1. What is Dart?
  2. Your first program
  3. dart run
  4. Comments
  5. String interpolation
  6. Summary - Dart basics

2 Variables

  1. var and type
  2. final
  3. const
  4. late
  5. Null safety
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and String
  4. Type inference
  5. dynamic
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Null-aware operators
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String interpolation
  3. length and methods
  4. substring
  5. contains and indexOf
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Pattern matching
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. for-in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Lists

  1. Creating lists
  2. List access
  3. add and remove
  4. length and contains
  5. List methods
  6. Summary - Lists

11 Sets and Maps

  1. Set
  2. Set operations
  3. Map
  4. Map operations
  5. Map iteration
  6. Summary - Sets and Maps

12 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Optional parameters
  5. First-class functions
  6. Summary - Functions

13 Null safety in depth

  1. Nullable types
  2. Null-aware operators
  3. The ! operator
  4. late
  5. Null check
  6. Summary - Null safety

14 Class basics

  1. class
  2. Constructor
  3. Instance variables
  4. Methods
  5. this
  6. Summary - Class basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. split and join
  2. replace
  3. trim and pad
  4. RegExp
  5. StringBuffer
  6. Summary - Advanced strings

17 Enums

  1. Defining enums
  2. Enum values
  3. Enhanced enums
  4. switch with enum
  5. Enum and patterns
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. The Exception class
  5. on clause
  6. Summary - Exceptions

19 Async basics

  1. Future
  2. async/await
  3. then
  4. Future.error
  5. Future.wait
  6. Summary - Async basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together