- create a new flutter project
flutter create flutter_project_name- install packages (already writtin in the pubspec = similar to npm install
flutter packages get- types
int, double, num, void, String, null, Function, enum, List, boolean
- every class is also a type
- variables
var, types
- classes
-
inheritance: extends => this class is based on other class
-
variables inside classes are called properties
-
functions inside classes are called methods
- class Constructor
void main(){
var jaehyuk = Person("Jaehyuk", 2);
print(jaehyuk);
}
class Person{
String? name;
int? age;
Person(String inputName, int age){
name = inputName;
this.age = age;
}
}
- import dependency
import "package:packageName/file.dart- positional argument vs named argument
*** all named argument is by default optional => hence to make it required, add required keyword
void main(){
var jaehyuk = Person(inputName: 'jaehyuk', age: 2 );
print(jaehyuk);
}
class Person{
String? name;
int? age;
Person({required String inputName, required int age}){
name = inputName;
this.age = age;
}
}
class Person {
String? name;
int? age;
Person({required this.name, this.age});
}
- invoking function using anonymous function
Column(
children: <Widget>[
const Text("This Question:"),
ElevatedButton(
// ignore: avoid_print
onPressed: () => answerQuestion("1"),
child: const Text("Answer 1"),
),
ElevatedButton(
// ignore: avoid_print
onPressed: () => answerQuestion("2"),
child: const Text("Answer 2"),
),
ElevatedButton(
// ignore: avoid_print
onPressed: () => answerQuestion("3"),
child: const Text("Answer 3"),
),
],
),- array
var questions = <String>[
"What's is your favorite color?",
"What's your favorite animal"
];
questions[0]
questions.elementAt(0)
// this is because array in dart is an object- states & stateful widget
- extends StatefulWidget
class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
State<StatefulWidget> createState() {
return MyAppState();
}
}- create NameState class
class MyAppState extends State<MyApp>{}here, State is a generic class type
- initialize state and a function that modifies the state
class MyAppState extends State<MyApp>{
var questionIndex = 0;
void answerQuestion(String question) {
// when updating state, always use setState method/ function
setState(() {
if (questionIndex == 0) {
questionIndex = questionIndex + 1;
}
});
// ignore: avoid_print
print(questionIndex);
}
}
-
private property => make sure somethings (properties + methods) inside the class cannot be manipulated externallly. => underscore is a dart convention that makes it private (only be accessed within the current file)
-
custom widget => common practice is to have just one widget per file => use "st" shortcut to create stateless or stateful widget
-
immutable warning => add final to property => final: cannot be reassigned (once build)
-
"Lifting the state up" => to manage the state on the shared, on the common denominator
-
Callback => passing function to a class constructor or anther function as a argument => why "callback": because the receiving widget/ class calls it in the future
-
final vs const => const variables are compile-time constants, meaning that their values must be known at compile time. const variables are also single-assignment, just like final variables. However, because their values are known at compile time, they cannot be assigned a value that is determined at runtime. =>In general, you should use final for variables whose values are determined at runtime, while const should be used for variables whose values are known at compile time. => runtime constant => which are initialized when app starts, but thereafter they dont change
var questions = [...]
questions = []
// this is not possible
const questions = [...]
questions = []
// no error during compilation (while coding), but throws error when run time
var questions = const [...]
questions = []
-
Getter => it is a mixture of property and a method
-
wrapping widgets (vsc extension) => Just right-click on a widget and press "Refactor".