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Does having a private constructor on a value class negate the benefits of a value class?


Does having a private constructor on a value class negate the benefits of a value class?

By : user2954721
Date : November 22 2020, 10:31 AM
hop of those help? If "treat as a primitive" here means "avoid allocation", then this indeed will not work, but not because of a private constructor.
As mentioned in Value Classes Guied
code :
def identity[T](t: T): T = t
identity(Meter(5.0))


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Don't the Ruby methods instance_eval() and send() negate the benefits of private visibility?

Don't the Ruby methods instance_eval() and send() negate the benefits of private visibility?


By : Steve Shi
Date : March 29 2020, 07:55 AM
this will help If you really want to protect instances of Widget, you can do this (and a bunch of other stuff; the code here is not a complete security solution, merely indicative):
code :
class Widget

  def some_public_method
    ...
  end

  private

  def utility_method
    ...
  end

  def send(method, *args, &block)
    raise NotImplementedError.new('Widget is secure. Stop trying to hack me.')
  end

  def instance_eval(&block)
    raise NotImplementedError.new('Widget is secure. Stop trying to hack me.')
  end

  class <<self
    private
    def class_eval(&block)
      raise NotImplementedError.new('Widget is secure. Stop trying to hack me.')
    end
  end
end

Widget.freeze
C# - Mixing of Private Constructor and non-private parameterful constructor are allowed in same class?

C# - Mixing of Private Constructor and non-private parameterful constructor are allowed in same class?


By : user1438139
Date : March 29 2020, 07:55 AM
I wish this helpful for you Private constructors don't only prevent instantiation from the outside world - they often enable construction from within the class. Indeed, the only reason a private constructor is often used to prevent instantiation is to avoid the compiler adding a public parameterless constructor by default. That's the only way in which a private constructor hinders other callers.
For example, suppose you have a class which needs to accept a collection in its constructor. A public constructor may always act defensively, copying the collection. However, you may have certain cases where the code within the class wants to create a new instance and knows that it doesn't need to copy the collection, just the reference. That's just one situation in which a private constructor makes a lot of sense.
What is the difference between a class having private constructor and a sealed class having private constructor?

What is the difference between a class having private constructor and a sealed class having private constructor?


By : 김대현
Date : March 29 2020, 07:55 AM
like below fixes the issue Yes A can be inherited by a nested class, while B cannot be inherited at all. This is perfectly legal:
code :
public class A {
  private A() { }

  public class Derived : A { }
}
public abstract class A {
  private A() { }

  public abstract void DoSomething();

  private class OneImpl : A { 
    public override void DoSomething() { Console.WriteLine("One"); }
  }

  private class TwoImpl : A { 
    public override void DoSomething() { Console.WriteLine("Two"); }
  }

  public static readonly A One = new OneImpl();
  public static readonly A Two = new TwoImpl();
}
abstract class with default constructor and class with private constructor difference

abstract class with default constructor and class with private constructor difference


By : rraut
Date : March 29 2020, 07:55 AM
I wish did fix the issue.
what's the difference between an Abstract class with a default constructor and a class with private constructor?
Exposing a class with a constructor containing a nested private class in constructor using Boost Python

Exposing a class with a constructor containing a nested private class in constructor using Boost Python


By : Girish
Date : March 29 2020, 07:55 AM
hop of those help? The whole point of the pimpl idiom is that it's private and completely transparent to the users of the class. You don't expose it.
What you do need to do is make it clear that A isn't copyable:
code :
class_<A, noncopyable>("A", init<>())
    .def("B", &A::B)
;
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