Opérations sur le système de fichiers

Sometimes, your app needs to store data directly on the device. This is where file system operations come in! Unlike shared_preferences (for small key-value data) or sqflite (for structured data), file system operations allow you to manage files directly.

You can store larger pieces of data, like images, audio, or custom formatted text files, that don't fit well into a database or simple key-value pairs.

Before you can read or write files, your app needs to know where it can store them. Flutter provides the path_provider package to help you find common directory paths safely across different platforms (iOS, Android, web, desktop).

• Application Documents Directory: This is where your app can store user-specific data that should persist.
• Temporary Directory: For data that doesn't need to persist across app launches, like cached files.

Let's use path_provider to get the application documents directory. Remember to add path_provider to your pubspec.yaml first!

dependencies:
flutter:
sdk: flutter
path_provider: ^2.0.11

Once you have a directory path, you can create a File object. This object represents the file at that specific path on the device's storage. It doesn't mean the file actually exists yet, it's just a reference.

You'll combine the directory path with your desired filename to construct the full file path.

Here's how you can combine the application documents path with a filename to create a File object. We'll use a simple text file name for our example.

The File object provides methods to write data. The most common ones are writeAsString() for text and writeAsBytes() for binary data. These operations are asynchronous, so you'll use await.

• writeAsString(String contents, {FileMode mode = FileMode.write}): Writes text. FileMode.write overwrites, FileMode.append adds to the end.
• writeAsBytes(List<int> bytes, {FileMode mode = FileMode.write}): Writes raw bytes.

Let's write some text content to our my_data.txt file. If the file doesn't exist, writeAsString will create it. If it does exist, it will overwrite its content by default.

Just as you can write, you can also read content back from files. The readAsString() method is perfect for text files, while readAsBytes() is used for binary data.

It's good practice to check if a file exists() before trying to read from it to prevent errors.

Now, let's read the content we just wrote back from my_data.txt. We'll first check if the file exists to be safe.

When data is no longer needed, you can delete files from the device's storage. The delete() method on a File object will remove it. This operation is also asynchronous.

Be careful when deleting files, as this action is usually irreversible!

Which of the following statements about Flutter file system operations are TRUE?

Great job! In this lesson, you've learned how to interact with the device's file system in Flutter:

• Used path_provider to find appropriate storage directories.
• Created File objects to reference specific files.
• Wrote content to files using writeAsString().
• Read content from files using readAsString().
• Understood how to delete files with delete().

File system operations are crucial for storing large, custom-formatted, or sensitive data directly on the device. Next, you can explore more advanced data handling or move on to other Flutter topics!