DEV Community: Hosain Mohamed

The main 3 point of Null safety in Flutter

Hosain Mohamed — Tue, 05 Oct 2021 05:58:24 +0000

This is would be a quick summary of null safety, explained in 3 points.

1- Question mark (?)

2- Exclamation mark (!)

3- late keyword

1 - Question mark (?) = Nullable
This can be used to tell compiler that this variable can be null.

String? name ;

If (?) is removed there would be a compiler error. as this variable could be null.

2 - exclamation mark (!) = Non Nullable
When converting from String ? (nullable string) to String
there would be no error as (nullable string) can contain a
value or can be null.

String name = "ahmed"; (Non nullable)
String? newName = name; 👌👌

The problem when converting from String to String ? (nullable
string) as String cannot contain a null value.

String? name ; (Nullable)
String newName = name; 🤦‍♂️🤦‍♂️ (Compiler error )

And this can be solved in 3 ways :
1 -

String? name ;
if( name!=null ){
String newName = name;
}

2-
String? name ;
String newName = name ?? "ahmed";

3-
String? name ;
String newName = name !;

last solution is using (!) when we tell the compiler that
name cannot be null and you should be sure of that and this
is preferred to be used under restricted condition otherwise
there would be a runtime error if name is null.

3- late keyword
This is simply can be used when you assign a value to a variable but later on like when you do in initState() function.

late String name ;
void initState() {
name = "ahmed"

super.initState();
}

Hope this was a helpful review on Null safety principles in Flutter.
Thank you for reading.

Open source Chat application with flutter and firebase

Hosain Mohamed — Thu, 18 Mar 2021 12:25:47 +0000

Hello Every one I build an open source chat application using Flutter framework and firebase as a backend.

Features :

Sign in - SignUp - logout .
linking with Firebase Authentication system.
client and backend validation during logging and register.
search by name of users.
real-time send and receive messages using stream and linking with Firebaes Firestore database.
viewing profile page and able to edit info and upload images.
use pagination for showing the messages and also for friends list.
nice looking UI and user-friendly animation with a splash screen at the beginning.
using Bloc for state management.
using Get-it as a Service Locator for dependency injection.

This project is a starting point for a Flutter application.

This is the Github link

https://github.com/hosain-mohamed/Flutter-chat-App

New Package Curved Splash screen

Hosain Mohamed — Wed, 17 Mar 2021 20:37:39 +0000

Hello everyone, I made a new package called curved_splash_screen

https://pub.dev/packages/curved_splash_screen

https://github.com/hosain-mohamed/curved_splash_screen

It is splash screen with curved custom bottom sheet and dots indicator within it.
You can add your custom splash screens according to it's index.
You can change any color of the items of the bottom sheet.
You can specify the text of back and skip button and their color.
All items in the bottom sheet is responsive to the screen size.

Don't forget to like it. If you have any modifications let me know.

Thanks & regards