错误：尝试添加初始化表达式，或在此构造函数中添加字段初始化器，或将其标记为“迟到”

html5 • • 问答 

void main() {
  Car c1 = new Car('E1001');
}

class Car {
  String engine;
  Car(String engine) {
    this.engine = engine;
    print("The engine is : ${engine}");
  }
}

回答

在飞镖零安全功能中，

  1. 要么使引擎变量可以为空?，

    class Car {
  String? engine;
  Car(String engine){
     this.engine = engine;
     print("The engine is : ${engine}");
  }
}

  2. 或者添加late关键字来懒惰地初始化它，

    class Car {
  late String engine;
  Car(String engine){
     this.engine = engine;
     print("The engine is : ${engine}");
  }
}

  3. 或者在构造函数的初始化块中初始化变量。

    class Car {
  String engine;
  Car(String engine) : engine = engine {
     print("The engine is : ${engine}");
  }
}
以上是错误：尝试添加初始化表达式，或在此构造函数中添加字段初始化器，或将其标记为“迟到”的全部内容。
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