In this lesson, we will cover Interfaces and Mixins. Interfaces act as a contract containing properties and methods that a class must define once it “implements” this interface. Mixins are Dart’s way of sharing properties and methods from multiple classes, since by design Dart adopts a single-inheritance model.

 

Abstract class:

void main() {  var pixel = Phone('Pixel XL', 'HTC');  pixel.getDeviceInfo();}abstract class Device {  String name;  String manufacturer;  void getDeviceInfo();}class Phone implements Device {  String name;  String manufacturer;    void getDeviceInfo() => print('''  ===  Device name: $name  Manufactured by: $manufacturer  ''');    Phone(this.name, this.manufacturer);}

　　

Define a mixin:

mixin FeaturesMixin {  bool blueTooth = true;  bool dualSim = false;  bool nfc = true;}

 

Extends a mixin:

// Extends FeaturesMixinmixin UtilitiesMixin on FeaturesMixin {  bool calculator = true;  bool flashlight = true;  bool thermometer = false;    String _has(bool feat) => feat ? 'Yes': 'No';    void getAllFeatures() => print('''  --FEATURES--    Bluetooth: ${_has(super.blueTooth)}  Dual SIM: ${_has(super.dualSim)}  NFC: ${_has(super.nfc)}  Calculator: ${_has(calculator)}  Flashlight: ${_has(flashlight)}  Thermometer: ${_has(thermometer)}  ===  ''');}

 

use Mixin:

class Phone with FeaturesMixin, UtilitiesMixin implements Device {

 

--

void main() {  var pixel = Phone('Pixel XL', 'HTC');  pixel.getDeviceInfo();  pixel.getAllFeatures(); /*  ===  Device name: Pixel XL  Manufactured by: HTC    --FEATURES--    Bluetooth: Yes  Dual SIM: No  NFC: Yes  Calculator: Yes  Flashlight: Yes  Thermometer: No  ===  */}mixin FeaturesMixin {  bool blueTooth = true;  bool dualSim = false;  bool nfc = true;}// Extends FeaturesMixinmixin UtilitiesMixin on FeaturesMixin {  bool calculator = true;  bool flashlight = true;  bool thermometer = false;    String _has(bool feat) => feat ? 'Yes': 'No';    void getAllFeatures() => print('''  --FEATURES--    Bluetooth: ${_has(super.blueTooth)}  Dual SIM: ${_has(super.dualSim)}  NFC: ${_has(super.nfc)}  Calculator: ${_has(calculator)}  Flashlight: ${_has(flashlight)}  Thermometer: ${_has(thermometer)}  ===  ''');}abstract class Device {  String name;  String manufacturer;  void getDeviceInfo();}class Phone with FeaturesMixin, UtilitiesMixin implements Device {  String name;  String manufacturer;    void getDeviceInfo() => print('''  ===  Device name: $name  Manufactured by: $manufacturer  ''');    Phone(this.name, this.manufacturer);}