Flutter - Dart的interface

在這裏看原文。

看這些教程的時候最好是打開dartpad。直接在裏面把這些代碼輸入進去看結果。這是dart官方提供的一個練習dart的地方。邊看邊練事半功倍。

正文

• 接口（interface）定義了每一個實現這個接口的類都須要遵照的「規則」。
• 當一個類實現（implements）一個接口的手，它必須override接口裏的每個方法和實例變量。
• 然而，Dart不支持聲明一個接口的語法。這些類聲明自己就是接口聲明。
• 任何的類均可以當作接口。要實現這個「接口」只要用implements關鍵字就能夠。
• 一旦一個類被用做接口，就必需要override全部的實例方法和實例成員。簡單來講就是實現類要從新定義全部的實例方法和實例成員。

聲明「接口」的語法

class interface_nasme {
    //...
}

class class_name implements interface_name {
    //...
}

例如：

class Person {
  
  void walk() {
    print("Person can walk");
  }

  void talk() {
    print("Person can talk");
  }
}
class Jay implements Person {
  
  @override
  void walk() {
    print("Jay can walk");
  }

  @override
  void talk() {
    print("Jay can talk");
  }
}

main() {
  Person person = new Person();
  Jay jay = new Jay();

  person.walk();
  person.talk();

  jay.walk();
  jay.talk();
}

輸出：

Person can walk
Person can talk
Jay can walk
Jay can talk

實現多個接口

Dart不支持多繼承，可是能夠實現多個接口。

class class_name implements intgerface1, interface2 //,...

例如：

class Person {
  String name;

  void ShowName() {
    print("My name is $name");
  }

  void walk() {
    print("Person can walk");
  }

  void talk() {
    print("Person can talk");
  }
}

class Viveki {
  String profession;

  void ShowProfession() {
    print("from class Viveki my profession is $profession");
  }
}

class Jay implements Person, Viveki {
  @override
  String profession;

  @override
  void ShowProfession() {
    print("from class Jay my Profession is $profession");
  }
  
  @override 
  String name; 
 
  @override 
  void ShowName() { 
    print("From class Jay my name is $name"); 
  } 
 
  @override 
  void walk() { 
    print("Jay can walk"); 
  } 
 
  @override 
  void talk() { 
    print("Jay can talk"); 
  } 
} 
 
main() { 
  Person person = new Person(); 
  Jay jay = new Jay(); 
  Viveki viveki = new Viveki(); 
 
  person.walk(); 
  person.talk(); 
  person.name = "Person"; 
  person.ShowName(); 
 
  print(""); 
 
  jay.walk(); 
  jay.talk(); 
  jay.name = "JAY"; 
  jay.profession = "Software Development"; 
  jay.ShowProfession(); 
  jay.ShowName(); 
 
  print(""); 
 
  viveki.profession = "Chemical Engineer"; 
  viveki.ShowProfession(); 
}

output:

Output
Person can walk
Person can talk
My name is Person

Jay can walk
Jay can talk
from class Jay my Profession is Software Development
From class Jay my name is JAY

from class Viveki my profession is Chemical Engineer