dart 多继承、抽象类

多继承
	with
		class X with a,b{
			...
		}
	也可以
		class X extends c with a,b{
			...
		}

抽象类:
抽象类不能实例化,继承必须实现内部方法

abstract class x{
	void f();
}

代码示例:

 void main(){
   People p =new People();
   p.people();

   A a=new A();
   a.say();
 }
 
 class Eat{
   void eat(){
     print('eat');
   }
 }

  class Sleep{
    void sleep()
    {
      print('sleep');
    }
  }

  class People with Eat,Sleep{
    void people(){
      eat();
      sleep();
    }
  }

  //抽象
  abstract class Animal{
    void say();
  }

  class A extends Animal{
    void say(){
      print('aa');
    }
  }