Null safety example: A CLI app for calculating lix

This is a small code example of an app that calculates the 'lix' readability index for a text file. The implementation uses the Dart null safety feature, and is meant to demonstrate how this feature works in a practical example.

Supported SDK versions

The example requires Dart 2.12 or later. If you're using Flutter, you need Flutter 2.0 or later.

Running from the terminal / command prompt

To run the main app, type these commands in the terminal/command-prompt:

$ cd <folder with samples repo>/null_safety/calculate_lix/
$ dart pub get
$ dart run bin/main.dart text/lorem-ipsum.txt

Next steps

Once you have the code running, here some suggestions for things to try:

• In lib/lix.dart line 30, try to remove the required keyword from one or more fields in the constructor, and notice the error shown.

• In lib/lix.dart line 49, try to delete the code that initializes one or more fields (e.g. words: words) and notice the error shown.

• In lib/lix.dart line 9, try to make words a nullable variable (int? words), and notice how we don't get errors about not checking for null in the _calculate() method.

• In lib/lix.dart line 22, try to remove the late keyword from readability, and notice how we get an error in the constructor.