Thread by @SandroMaglione

What if your #flutter app fails? Should you throw? Error? Exception?

#dart gives you both Error and Exception 🎯

But how do they work? Which one should you choose? 🤔

Here is the answer 👇🧵

Error & Exception ‼️

#dart has both of them, but they are not the same 💁🏼‍♂️

👉 Exceptions: conditions that you can plan ahead for *and catch*

👉 Errors: conditions that *you don’t expect*

Exceptions should be handled in your code 💻

You (developer 💁🏼‍♂️) know that they can happen, and so you plan accordingly

👉 *It is intended to be caught*

👉 It should contain useful data fields

👉 Should not crash the app

Is good practice to define a custom exception by implementing the Exception interface

Give it meaningful information and a readable message 💡

#dart has a good set of tools for Exceptions

☑️ try
☑️ catch
☑️ catch (on)
☑️ StackTrack
☑️ finally
☑️ rethrow

Example of Exceptions

👉 FormatException

👉 IOException

👉 TimeoutException

Errors represents a program failure 💥

These are not expected

If they occur, the program is erroneous, and terminating the program may be the safest response 💆‍♂️

Example: `String.contains`

‼️ `startIndex` must not be negative or greater than `length`

There is clearly an error in your program if you call `'ABC'.contains('A', -10)` 💁🏼‍♂️

Note ℹ️

Error objects are also used for system wide failures like stack overflow or an out-of-memory situation

Example of Errors

👉 NoSuchMethodError

👉 StackOverflowError

👉 UnimplementedError

There is a lot behind all of these, here the docs for Exceptions 📃

dart.dev/guides/languag…

Error handling is hard but absolutely crucial for any app

And there is much more to discover 🗺

Follow @SandroMaglione (me 👋) for more about #dart and #flutter