英文:
Make property in abstract class only settable in constructor of child class?
问题
我在一个具体类中有一个仅支持get的属性。根据定义，该属性只能在该类的构造函数中设置。后来我决定将这个属性放到一个没有构造函数的抽象类中，而具体类继承自该抽象类。如何使现在在抽象类中的属性只能在子类的构造函数中设置？
不会起作用的解决方案：
- 如果我给属性添加
protected set修饰符，那么子类将具有比我要求的更多权限。 init不是一个选项，因为我只想在构造函数中设置它。readonly不一定会起作用，因为我使用的是C# 7.3。
示例原始类：
public class FooOriginal
{
public int IntHere { get; }
}
示例抽象类：
public abstract class FooAbstract
{
public int IntHere { get; }
}
示例子类：
public class FooChild : FooAbstract
{
public FooChild()
{
// 不会编译，因为IntHere是只读的。
intHere = 3;
}
}
英文:
I have a get-only property in a concrete class. By definition, that can only be set in a constructor of that class. I later decide that I want this property to belong to a constructor-less abstract class that the concrete class inherits from. How can I make the property that is now in the abstract class only capable of being set within the constructors of the child classes?
Solutions that won't work:
- If I give the property a
protected setmodifier, then allows the child class more power than I'm asking for. initisn't an option because I only want it set in the constructor.readonlywon't always work, because I'm on C# 7.3.
Example original class:
public class FooOriginal
{
public int IntHere { get; }
}
Example abstract class:
public abstract class FooAbstract
{
public int IntHere { get; }
}
Example child class
public class FooChild : FooAbstract
{
public FooChild()
{
// Won't compile because IntHere is get-only.
intHere = 3;
}
}
答案1
得分: 4
为了实现这一点，您可以给基类添加一个构造函数，如果您喜欢，可以将其设置为protected：
public abstract class FooAbstract
{
public int IntHere { get; }
protected FooAbstract(int intHere)
{
IntHere = intHere;
}
}
然后，您的旧类可以调用基类构造函数，例如：
public class FooOriginal : FooAbstract
{
public FooOriginal(int intHere)
: base(intHere) // <-- 这就是魔法
{
}
}
或者，如果您想按照您的示例传递一个常量值：
public FooOriginal() : base(3)
{
}
英文:
To achieve this, you can give the base class a constructor, you can make it protected if you like:
public abstract class FooAbstract
{
public int IntHere { get; }
protected FooAbstract(int intHere)
{
IntHere = intHere;
}
}
And your old can call the base class constructor, for example:
public class FooOriginal : FooAbstract
{
public FooOriginal(int intHere)
: base(intHere) // <-- This is the magic
{
}
}
Or if you want to pass in a constant value as per your example:
public FooOriginal() : base(3)
{
}
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