- Dart represents arrays in the form of List objects.
- List is simply an ordered group of objects.
Example 1 [Getting Name]
void main() {
List<String> myList = [
'List1',
'List2',
'List3',
'List4'
];
print(myList[0]);
}Example 2 [Getting Index Value]
void main() {
List<String> myList = [
'List1',
'List2',
'List3',
'List4'
];
print(myList.indexOf('List1'));
myList.add('List5'); // For adding an item
myList.insert(1,'List'); // For adding the item in specific position
}main.dart
import 'package:flutter/material.dart';
void main() => runApp(Quizzler());
class Quizzler extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.grey.shade900,
body: SafeArea(
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 10.0),
child: QuizPage(),
),
),
),
);
}
}
class QuizPage extends StatefulWidget {
@override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
List<Icon> mStoreKeeper = [
Icon(
Icons.check,
color: Colors.green,
),
Icon(
Icons.close,
color: Colors.red,
),
Icon(
Icons.close,
color: Colors.red,
),
Icon(
Icons.close,
color: Colors.red,
)
];
@override
Widget build(BuildContext context) {
return Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
flex: 5,
child: Padding(
padding: EdgeInsets.all(10.0),
child: Center(
child: Text(
'This is where the question text will go.',
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 25.0,
color: Colors.white,
),
),
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
textColor: Colors.white,
color: Colors.green,
child: Text(
'True',
style: TextStyle(
color: Colors.white,
fontSize: 20.0,
),
),
onPressed: () {
setState(() {
mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
color: Colors.red,
child: Text(
'False',
style: TextStyle(
fontSize: 20.0,
color: Colors.white,
),
),
onPressed: () {
setState(() {
mStoreKeeper.add(Icon(
Icons.close,
color: Colors.red,
));
});
},
),
),
),
Row(
children: mStoreKeeper,
)
],
);
}
}- A template (blueprint) for creating objects (the real thing) that we're going to showing in our app.
- A class has two important things (i.e.) Properties and Methods.
- Example: If we take a car color and numberOfSeats is properties and drive(), break() is Methods.
- It is a basic unit of Object Oriented Programming and represents the real life entities.
- For example, we can take a Car -> Car is an object.
Creating the Class
class car {
int numberOfDoors = 5;
void drive(){
print('wheels start turning');
}
}- where int numberOfDoors = 5 is the varaible(i.e.) Properties and void drive() is the function(i.e.) Methods
Creating an Object from the Class
Car myCar = Car();- where int Car = 5 is the type, myCar is the object and Car() is the new version of that class.
Example
void main(){
Human mHuman = Human();
print(mHuman.height);
mHuman.height = 2.0;
print(mHuman.height);
}
class Human{
double height = 1.0;
int age = 60;
}Using constructor
void main(){
Human mHuman = Human(mHeight: 10.0);
print(mHuman.height);
mHuman.talk('Hello World');
}
class Human{
double height;
int age = 60;
Human({double mHeight}){
height = mHeight;
}
void talk(String mStringText){
print(mStringText);
}
}main.dart
import 'package:flutter/material.dart';
void main() => runApp(Quizzler());
class Quizzler extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.grey.shade900,
body: SafeArea(
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 10.0),
child: QuizPage(),
),
),
),
);
}
}
class QuizPage extends StatefulWidget {
@override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
List<Icon> mStoreKeeper = [];
List<String> mQuestions = [
'You can lead a cow down stairs but not up stairs.',
'Approximately one quarter of human bones are in the feet.',
'A slug\'s blood is green.'
];
List<bool> mAnswers = [false, true, true];
int mQuestionNumber = 0;
@override
Widget build(BuildContext context) {
return Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
flex: 5,
child: Padding(
padding: EdgeInsets.all(10.0),
child: Center(
child: Text(
mQuestions[mQuestionNumber],
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 25.0,
color: Colors.white,
),
),
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
textColor: Colors.white,
color: Colors.green,
child: Text(
'True',
style: TextStyle(
color: Colors.white,
fontSize: 20.0,
),
),
onPressed: () {
bool mCorrectAnswer = mAnswers[mQuestionNumber];
if (mCorrectAnswer == true) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuestionNumber += 1;
mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
color: Colors.red,
child: Text(
'False',
style: TextStyle(
fontSize: 20.0,
color: Colors.white,
),
),
onPressed: () {
bool mCorrectAnswer = mAnswers[mQuestionNumber];
if (mCorrectAnswer == false) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuestionNumber++;
mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Row(
children: mStoreKeeper,
)
],
);
}
}Question.dart
class Question {
String mQuestionText;
bool mAnswerValue;
Question({String mQ, bool mA}) {
mQuestionText = mQ;
mAnswerValue = mA;
}
}- Abstraction is a process of hiding the implementation details and showing only functionality to the user.
- It can have abstract and non-abstract methods (method with the body).
- In other words, Split up the functionality in to different Component.
main.dart
import 'package:flutter/material.dart';
import 'quiz_brain.dart';
QuizBrain mQuizBrain = QuizBrain();
void main() => runApp(Quizzler());
class Quizzler extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.grey.shade900,
body: SafeArea(
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 10.0),
child: QuizPage(),
),
),
),
);
}
}
class QuizPage extends StatefulWidget {
@override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
@override
Widget build(BuildContext context) {
return Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
flex: 5,
child: Padding(
padding: EdgeInsets.all(10.0),
child: Center(
child: Text(
mQuizBrain
.mQuestionList[mQuizBrain.mQuestionNumber].mQuestionText,
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 25.0,
color: Colors.white,
),
),
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
textColor: Colors.white,
color: Colors.green,
child: Text(
'True',
style: TextStyle(
color: Colors.white,
fontSize: 20.0,
),
),
onPressed: () {
bool mCorrectAnswer = mQuizBrain
.mQuestionList[mQuizBrain.mQuestionNumber].mAnswerValue;
if (mCorrectAnswer == true) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuizBrain.mQuestionNumber += 1;
mQuizBrain.mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
color: Colors.red,
child: Text(
'False',
style: TextStyle(
fontSize: 20.0,
color: Colors.white,
),
),
onPressed: () {
bool mCorrectAnswer = mQuizBrain
.mQuestionList[mQuizBrain.mQuestionNumber].mAnswerValue;
if (mCorrectAnswer == false) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuizBrain.mQuestionNumber++;
mQuizBrain.mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Row(
children: mQuizBrain.mStoreKeeper,
)
],
);
}
}quiz_brain.dart
import 'package:flutter/material.dart';
import 'Question.dart';
class QuizBrain {
List<Icon> mStoreKeeper = [];
List<Question> mQuestionList = [
Question('Some cats are actually allergic to humans', true),
Question('You can lead a cow down stairs but not up stairs.', false),
Question('Approximately one quarter of human bones are in the feet.', true),
Question('A slug\'s blood is green.', true),
Question('Buzz Aldrin\'s mother\'s maiden name was \"Moon\".', true),
Question('It is illegal to pee in the Ocean in Portugal.', true),
Question(
'No piece of square dry paper can be folded in half more than 7 times.',
false),
Question(
'In London, UK, if you happen to die in the House of Parliament, you are technically entitled to a state funeral, because the building is considered too sacred a place.',
true),
Question(
'The loudest sound produced by any animal is 188 decibels. That animal is the African Elephant.',
false),
Question(
'The total surface area of two human lungs is approximately 70 square metres.',
true),
Question('Google was originally called \"Backrub\".', true),
Question(
'Chocolate affects a dog\'s heart and nervous system; a few ounces are enough to kill a small dog.',
true),
Question(
'In West Virginia, USA, if you accidentally hit an animal with your car, you are free to take it home to eat.',
true),
];
int mQuestionNumber = 0;
}Question.dart
class Question {
String mQuestionText;
bool mAnswerValue;
Question(String mQ, bool mA) {
mQuestionText = mQ;
mAnswerValue = mA;
}
}- Binding (or wrapping) code and data together into a single unit are known as encapsulation..
- The whole idea behind encapsulation is to hide the implementation details from users.
- If a data member is private it means it can only be accessed within the same class.
- No outside class can access private data member (variable) of other class.
- We can use setter and getter methods to set and get the data in it.
- By providing only a setter or getter method, you can make the class read-only or write-only.
main.dart
import 'package:flutter/material.dart';
import 'quiz_brain.dart';
QuizBrain mQuizBrain = QuizBrain();
void main() => runApp(Quizzler());
class Quizzler extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
backgroundColor: Colors.grey.shade900,
body: SafeArea(
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 10.0),
child: QuizPage(),
),
),
),
);
}
}
class QuizPage extends StatefulWidget {
@override
_QuizPageState createState() => _QuizPageState();
}
class _QuizPageState extends State<QuizPage> {
List<Icon> mStoreKeeper = [];
@override
Widget build(BuildContext context) {
return Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Expanded(
flex: 5,
child: Padding(
padding: EdgeInsets.all(10.0),
child: Center(
child: Text(
mQuizBrain.getQuestionText(),
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 25.0,
color: Colors.white,
),
),
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
textColor: Colors.white,
color: Colors.green,
child: Text(
'True',
style: TextStyle(
color: Colors.white,
fontSize: 20.0,
),
),
onPressed: () {
bool mCorrectAnswer = mQuizBrain.getAnswerText();
if (mCorrectAnswer == true) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuizBrain.nextQuestion();
mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Expanded(
child: Padding(
padding: EdgeInsets.all(15.0),
child: FlatButton(
color: Colors.red,
child: Text(
'False',
style: TextStyle(
fontSize: 20.0,
color: Colors.white,
),
),
onPressed: () {
bool mCorrectAnswer = mQuizBrain.getAnswerText();
if (mCorrectAnswer == false) {
print('The Answer is Correct');
} else {
print('The Answer is Wrong');
}
setState(() {
mQuizBrain.nextQuestion();
mStoreKeeper.add(Icon(
Icons.check,
color: Colors.green,
));
});
},
),
),
),
Row(
children: mStoreKeeper,
)
],
);
}
}quiz_brain.dart
import 'package:flutter/material.dart';
import 'Question.dart';
class QuizBrain {
int _mQuestionNumber = 0;
List<Question> _mQuestionList = [
Question('Some cats are actually allergic to humans', true),
Question('You can lead a cow down stairs but not up stairs.', false),
Question('Approximately one quarter of human bones are in the feet.', true),
Question('A slug\'s blood is green.', true),
Question('Buzz Aldrin\'s mother\'s maiden name was \"Moon\".', true),
Question('It is illegal to pee in the Ocean in Portugal.', true),
Question(
'No piece of square dry paper can be folded in half more than 7 times.',
false),
Question(
'In London, UK, if you happen to die in the House of Parliament, you are technically entitled to a state funeral, because the building is considered too sacred a place.',
true),
Question(
'The loudest sound produced by any animal is 188 decibels. That animal is the African Elephant.',
false),
Question(
'The total surface area of two human lungs is approximately 70 square metres.',
true),
Question('Google was originally called \"Backrub\".', true),
Question(
'Chocolate affects a dog\'s heart and nervous system; a few ounces are enough to kill a small dog.',
true),
Question(
'In West Virginia, USA, if you accidentally hit an animal with your car, you are free to take it home to eat.',
true),
];
void nextQuestion() {
if (_mQuestionNumber < _mQuestionList.length - 1) {
_mQuestionNumber++;
}
}
String getQuestionText() {
return _mQuestionList[_mQuestionNumber].mQuestionText;
}
bool getAnswerText() {
return _mQuestionList[_mQuestionNumber].mAnswerValue;
}
}Question.dart
class Question {
String mQuestionText;
bool mAnswerValue;
Question(String mQ, bool mA) {
mQuestionText = mQ;
mAnswerValue = mA;
}
}- Inheritance is the process by which objects of one class acquire the properties & methods of another class.
- It provides code reusability.
- It is used to achieve runtime polymorphism.
Example
void main(){
Monkey mMonkey = Monkey();
print(mMonkey.height);
mMonkey.talk('Hello World');
mMonkey.monkeWeight();
}
class Human{
double height = 10.0;
int age = 60;
void talk(String mStringText){
print(mStringText);
}
}
class Monkey extends Human{
double weight = 150.0;
void monkeWeight(){
print('Weight$weight');
}
}- Polymorphism allows us to perform a single action in different ways.
- The most common use of polymorphism in OOP occurs when a parent class reference is used to refer to a child class object.
- In Java, we use method overloading and method overriding to achieve polymorphism.
- Two types of polymorphism in Java: compile-time polymorphism and runtime polymorphism.
- Static Polymorphism also known as compile time polymorphism.
- Dynamic Polymorphism also known as runtime polymorphism.
Compiletime Polymorphism (or Static polymorphism)
- Static Polymorphism also known as compile time polymorphism.
- Static Polymorphism that is resolved during compiler time is known as static polymorphism.
- Method overloading is an example of compile time polymorphism.
Runtime Polymorphism (or Dynamic polymorphism)
- It is also known as Dynamic Method Dispatch.
- Dynamic polymorphism is a process in which a call to an overridden method is resolved at runtime, thats why it is called runtime polymorphism.
- Method overriding is an example of runtime polymorphism.
Example
void main(){
ElectricCar myElectricCar = ElectricCar();
myElectricCar.drive();
myElectricCar.recharge();
LevitatingCar myDrivingCar = LevitatingCar();
myDrivingCar.drive();
SelfDrivingCar mySelfDrivingCar = SelfDrivingCar('HangOver');
mySelfDrivingCar.drive();
}
class Car{
int numberOfSeats = 5;
void drive(){
print('Wheel Turn.');
}
}
class ElectricCar extends Car{
int batteryLevel = 100;
void recharge(){
batteryLevel = 100;
}
}
class LevitatingCar extends Car{
@override
void drive(){
print('glide forwards');
}
}
class SelfDrivingCar extends Car{
String mDestination;
SelfDrivingCar(String mUserDestination){
mDestination = mUserDestination;
}
@override
void drive(){
super.drive();
print('Sterring towards $mDestination');
}
}- Constructor is a block of code that initializes the newly created object.
- Constructor resembles an instance method in java but it’s not a method as it doesn’t have a return type.
- It is called when an instance of the class is created.
- At the time of calling constructor, memory for the object is allocated in the memory.
- It calls a default constructor if there is no constructor available in the class.
Example 1
void main(){
Human mKite = Human(height: 15, weight: 30.5);
print(mKite.height);
Human mJenny = Human(height: 25, weight: 13.5);
print(mJenny.height);
}
class Human{
double height;
double weight;
Human({double height,double weight}){
this.height = height;
this.weight = weight;
}
}Example 2
void main(){
Human mKite = Human(height: 15, weight: 30.5);
print(mKite.height);
Human mJenny = Human(height: 25, weight: 13.5);
print(mJenny.height);
}
class Human{
double height;
double weight;
Human({this.height,this.weight});
}- IF statement basically just checks to see if a condition is true then it carry out the instruction inside a set of curlybraces.
- Different types of Operators [ ==, !=, >, <, >=, <=, &&, ||, ! ]
if (mTrack == 'Clear'){
go();
} else {
print('...');
}Example
import 'dart:math';
void main() {
loveCalculator();
}
void loveCalculator(){
int loveScore = Random().nextInt(100) + 1;
print(loveScore);
if (loveScore > 70){
print('You Love Each Other very much');
} else if(loveScore > 50){
print('You Love Each Other');
} else{
print('You Love Each Other but have to understand');
}
}- Reduces a collection to a single value by iteratively combining each element of the collection with an exisitng value.
- Fold is also known as funtional operators.
Example using for loop
void main() {
final values = [1,2,3,4];
int result = 0;
for (int i= 0; i<values.length; i++){
result += values[i];
}
print(result);
// Simplified for loop
for (int value in values){
result += value;
}
print(result);
}Example using closures and the fold method
void main() {
final values = [1,2,3,4];
int mValues = values.fold(0, (result, value) => result + value);
print(mValues);
}- Computed Properties are the features of Dart language that can be used to define properties whose value is computed reather than stored.
- Getters and setters are special methods that provide explicit read and write access to an object's properties.
Example
abstract class Shape {
double get area;
}
class Square implements Shape{
Square({this.side});
final double side;
double get area => side * side;
}
void main(){
final square = Square(side: 10.0);
print(square.area);
}