void main() {
// Interfaces in dart
}
abstract class A {
String a;
void testA1();
void testA2() {
print("A2");
}
}
abstract class B {
void testB1();
void testB2() {
print("B2");
}
}
class C implements A, B {
@override
void testB1() {}
@override
void testB2() {}
@override
String a;
@override
void testA1() {}
@override
void testA2() {}
}
void main() {
// Interfaces in dart
}
class A {
String a;
void testA2() {
print("A2");
}
}
class B {
void testB2() {
print("B2");
}
}
class C implements A, B {
@override
void testB2() {}
@override
String a;
@override
void testA2() {}
}
Dart implicitly defines a class as an interface, hence called as implicit interface . As there is no interface keyword , implicitly all classes are interfaces .
Note: This might change in the future
You can implement multiple interfaces at once
Whenever you implement a interface you must override everything inside it
Interface : Why we use them -1 ?
import 'dart:math';
void main() {
// Interface is generally used with abstract Class
// Though dart gives us the flexibility to use it with
// normal class , most of the time it will be used with abstract class
double area(Shape shape){
return shape.calarea();
}
print(area(Square(10)));
}
abstract class Shape {
void draw();
double calarea();
}
class Circle implements Shape{
int radius;
@override
void draw() {
print("Drawing a Circle");
}
@override
double calarea() {
return pi*pow(this.radius,2);
}
Circle(this.radius);
}
class Square implements Shape {
double length;
@override
void draw() {
print("Drawing a Square");
}
@override
double calarea() {
return pow(this.length, 2);
}
Square(this.length);
Interface : Why we use them -2 ?
void main(){
var purchase1 = Purchase();
purchase1.pay(Bkash());
}
abstract class PaymentInterface{
void payment();
}
class Bkash implements PaymentInterface{
@override
void payment(){
print("Bkash");
// Logic for payment using Bkash
}
}
class Rocket implements PaymentInterface {
@override
void payment(){
print("Rocket");
// Logic for payment using Rocket
}
}
class Visa implements PaymentInterface{
@override
void payment(){
print("Visa");
// Logic for payment using Visa
}
}
class Cash implements PaymentInterface{
@override
void payment(){
print("Cash");
// Logic for payment using Cash
}
}
//--------------------
class Purchase{
void pay(PaymentInterface paymenttype){
paymenttype.payment();
//Payment Logic for a product purchase
}
}
void main(){
var purchase1 = Purchase();
purchase1.onlinepay(Bkash());
purchase1.pay(Bkash());
}
abstract class LoginInterface{
void login();
}
abstract class PaymentInterface{
void payment();
}
class Bkash implements PaymentInterface,LoginInterface{
@override
void login(){
print("login");
// Login logic for Bkash
}
@override
void payment(){
print("Bkash");
// Logic for payment using Bkash
}
}
class Rocket implements PaymentInterface,LoginInterface{
@override
void login(){
print("login");
// Login logic for Rocket
}
@override
void payment(){
print("Rocket");
// Logic for payment using Rocket
}
}
class Visa implements PaymentInterface{
@override
void payment(){
print("Visa");
// Logic for payment using Visa
}
}
class Cash implements PaymentInterface{
@override
void payment(){
print("Cash");
// Logic for payment using Cash
}
}
//--------------------
class Purchase{
void onlinepay(LoginInterface paymenttype){
paymenttype.login();
}
void pay(PaymentInterface paymenttype){
paymenttype.payment();
//Payment Logic for a product purchase
}
}
Though dart gives us the flexibility to implement any class , most of the time you are going to implement abstract classes containing abstract methods (i.e. turning those abstract classes into interfaces )
