Dart代码报错：非抽象类Vehicle未实现info成员方法

你遇到的错误提示明确指出，Vehicle类作为非抽象类，必须实现info成员。以下是四种解决方案的具体实现方式，你可以根据需求选择：

方案1：直接在Vehicle类中实现info方法 #

在Vehicle类里添加info方法的具体逻辑，比如打印车辆信息：

class Vehicle {
  String brand = "";
  String model = "";
  int horsePower = 0;

  Vehicle(this.brand, this.model, this.horsePower);

  // 添加info方法实现
  void info() {
    print("品牌: $brand，型号: $model，马力: $horsePower");
  }
}

方案2：通过父类或混入继承info实现 #

如果info方法的实现来自某个父类或混入类，直接让Vehicle继承或混入即可。比如有一个包含info实现的混入类：

mixin VehicleInfo {
  String get brand;
  String get model;
  int get horsePower;

  void info() {
    print("品牌: $brand，型号: $model，马力: $horsePower");
  }
}

// Vehicle类混入该类
class Vehicle with VehicleInfo {
  @override
  String brand = "";
  @override
  String model = "";
  @override
  int horsePower = 0;

  Vehicle(this.brand, this.model, this.horsePower);
}

方案3：将Vehicle标记为抽象类 #

把Vehicle改为抽象类，这样就无需自己实现info方法，转而让子类（Car、Motorcycle）去实现：

// 改为抽象类
abstract class Vehicle {
  String brand = "";
  String model = "";
  int horsePower = 0;

  Vehicle(this.brand, this.model, this.horsePower);

  // 声明抽象方法，由子类实现
  void info();
}

// 子类Car实现info方法
class Car extends Vehicle {
  Car(String brand, String model, int horsePower)
      : super(brand, model, horsePower);

  @override
  void info() {
    print("轿车 - 品牌: $brand，型号: $model，马力: $horsePower");
  }
}

// 子类Motorcycle实现info方法
class Motorcycle extends Vehicle {
  Motorcycle(String brand, String model, int horsePower)
      : super(brand, model, horsePower);

  @override
  void info() {
    print("摩托车 - 品牌: $brand，型号: $model，马力: $horsePower");
  }
}

方案4：实现noSuchMethod处理未定义方法 #

通过重写noSuchMethod来捕获info方法的调用，避免编译错误：

class Vehicle {
  String brand = "";
  String model = "";
  int horsePower = 0;

  Vehicle(this.brand, this.model, this.horsePower);

  @override
  dynamic noSuchMethod(Invocation invocation) {
    // 判断调用的是info方法
    if (invocation.memberName == #info) {
      print("info方法未实现，当前车辆信息：品牌$brand，型号$model，马力$horsePower");
      return null;
    }
    // 其他未定义方法交给父类处理
    return super.noSuchMethod(invocation);
  }
}

修改后的完整代码示例（以方案1为例） #

// Higher order and Lexure Closure
Function plusWith(num x) {
  return (num y) => x + y;
}

class Vehicle {
  String brand = "";
  String model = "";
  int horsePower = 0;

  Vehicle(this.brand, this.model, this.horsePower);

  // 实现info方法
  void info() {
    print("品牌: $brand，型号: $model，马力: $horsePower");
  }
}

class Car extends Vehicle {
  Car(String brand, String model, int horsePower)
      : super(brand, model, horsePower);
}

class Motorcycle extends Vehicle {
  Motorcycle(String brand, String model, int horsePower)
      : super(brand, model, horsePower);
}

main(List<String> args) {
//Lambda Functions

  var func1 = (int v1) => v1 * 3;
  print(func1(5));

// Lexure Closure Cont;

  var addNum1 = plusWith(5);
  var addNum2 = plusWith(7);

  print(addNum1(2)); // Output 5 + 2 = 7
  print(addNum2(3)); // Output 7 + 3 = 10

  Vehicle car = Car(brand: "Golf", model: "VW", horsePower: 150);
  Vehicle car2 = Car(model: "A4", brand: "Audi", horsePower: 150);
  Vehicle moto = Motorcycle(brand: "MT-25", model: "Yamaha", horsePower: 37);
  Vehicle moto2 =
      Motorcycle(brand: "Super-Tenere", model: "Yamaha", horsePower: 127);

  List<Vehicle> allVehicle = [car, car2, moto, moto2];
  var listOf = List<Vehicle>.of(allVehicle.whereType<Car>());

  print(listOf);
  // 可以调用info方法测试
  car.info();
}

内容的提问来源于stack exchange，提问作者Yiğit Yıldırım