Summary - File I/O

Combine readAsString, writeAsString and exists to write a notes app.

Summary: File I/O

In this group you saw the dart:io library, reading with readAsStringSync, writing with writeAsStringSync, existence checks with existsSync and folder operations with Directory. File operations give persistent data.

Now we combine them: we will write and read a notebook. This is a small persistent storage example.

Remember: writing overwrites by default; append adds to the end; an existence check prevents errors.

Exercise The notebook

Import the library with import 'dart:io';. In main create File('book.txt'). Write two lines with writeAsStringSync('line1\nline2'). Then read with readAsStringSync() and print it with print.

Show example solution

import 'dart:io';

void main() {
  var f = File('book.txt');
  f.writeAsStringSync('line1\nline2');
  print(f.readAsStringSync());
}

Test yourself

Concept matching

readAsStringSync()

Reading
writeAsStringSync()

Writing
existsSync()

Existence
Directory

Folder
What does writeAsStringSync do without a mode?
- Deletes the file
- Appends
- Throws
- Overwrites
Show answer

Overwrites — without a mode it overwrites.

The readAsStringSync call

var content = f.____();

Show answer

var content = f.readAsStringSync();

Next lesson: pub

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies