Error: Try adding an initializer expression, or add a field initializer in this constructor, or mark it 'late'

user_9172968 0
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void main() {
  Car c1 = new Car('E1001');
}

class Car {
  String engine;
  Car(String engine) {
    this.engine = engine;
    print("The engine is : ${engine}");
  }
}
dart flutter constructor
3 Answers

In the dart null-safety feature,

  1. either make the engine variable nullable by ?,

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

  2. or add the late keyword to initialise it lazily,

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

  3. or initialize the variable in the constructor's initialize block.

    class Car {
  String engine;
  Car(String engine) : engine = engine {
     print("The engine is : ${engine}");
  }
}
user_42318090

Update, for initialize the variable in the constructor's:

class Car{
    String name;
    int wights; 
    Car(this.name,this.wigths);
    Car.origin(): this.name='', this.wigths=0;
  }
user_152948810

Using late keyword you can make a null variable.

Ex: late String engine;

"?" used for making null value.

Ex: String? engine;

user_91729680
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