c# - 强制子类初始化字段

Question

我有一个抽象基类，其中包含一些字段和一些作用于这些字段的方法。例如:

public abstract class A
{
    protected double _field;

    public double SquaredField { get { return _field * _field; } }

    ... some other abstract methods
}

我想强制 A 的所有子级在其构造函数中初始化 _field

public class B : A
{
    public B(double field)
    {
         _field = Math.Sqrt(field);
    }

    ... some other method implementations
}

实现此目标的正确模式是什么？

-- 编辑

我最后做的是:

public abstract class A
{
    protected readonly double _field;

    public A(double field)
    {
         _field = field;
    }

    public double SquaredField { get { return _field * _field; } }

    ... some other abstract methods
}


public class B : A
{
    public B(double field) : base(field)
    {
    }

    public static B CreateNew(double val)
    {
         return new B(Math.Sqrt(field));
    }

    ... some other method implementations
}

Answer 1

根本不要向派生类公开字段。相反，创建一个 protected 抽象属性:

public abstract class A
{
    protected double Field { get; }

    public double SquaredField { get { return Field * Field; } }
}

或者，如果该字段对于特定实例应始终为常量，则将其设为构造函数参数并保持私有(private):

public abstract class A
{
    private readonly double _field;

    public double SquaredField { get { return _field * _field; } }

    protected A(double field)
    {
        _field = field;
    }
}