如何在构造函数上使用命名参数的Dart类中添加吸气剂？

Question

Suppose I have the following Dart class, with a named parameter in its constructor:

class TestClass {
  final int someValue;
  TestClass({this.someValue});
}

void someMethod() {
  TestClass testClass = new TestClass(someValue: 10);
  print(testClass.someValue);
}

How can I add a getter for the field? I was trying something along the lines of:

class TestClass {
  final int _someValue;
  TestClass({this.someValue});
  int get someValue => _someValue+2;
}

Answer 1

Named parameters can't be private, but you can get the results you want using a named parameter, a private member, and an initializer. You could do the same thing in the constructor body without the initializer, but then _someValue couldn't be final.

class TestClass {
  final int _someValue;

  TestClass({int someValue}) : _someValue = someValue;

  int get someValue => _someValue;
}

However, there is very little value to doing this in Dart. A getter without a corresponding setter is semantically equivalent to a final field.

Answer 2

TestClass({this.someValue});

There's no member variable by that name. Did you mean _someValue ?