Seald classes

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  • > Adrian
    #1

    Seald classes

    When classes are not being inherited from. Is there an advantage to be
    gained by making them "sealed", and, if so, what is that advantage?

    Thank you,
    Adrian.


    Tags: None
    • Jeroen
      #2
      Re: Seald classes

      Adrian < wrote:
      When classes are not being inherited from. Is there an advantage to be
      gained by making them "sealed", and, if so, what is that advantage?
      Maybe there's an advantage to think of, but as I learned it you seal
      classes to make sure nothing inherits from it, not that you seal
      classes that are not inherited from.

      -Jeroen

        Comment

        • Ciaran O''Donnell
          #3
          RE: Seald classes

          The could be a performance advantage as if the CLR KNOWs for definate that
          nothing is going to inherit and override methods it can make performance
          optimizations like methods inlining etc without any risk. It depends on you
          code and its structure and what optimizations your framework version has in
          it but it something shouldn't be inherited from then mark it as sealed.
          Is a class can be a base, make sure to mark only methods/fields that need to
          be protected and virtual as such.

          Ciaran O'Donnell



          "Adrian <" wrote:
          When classes are not being inherited from. Is there an advantage to be
          gained by making them "sealed", and, if so, what is that advantage?
          >
          Thank you,
          Adrian.
          >
          >
          >

            Comment

            • Bryan
              #4
              RE: Seald classes

              It simplifies the virtual method table. At compile time, it is not possible
              to determine the actual method that will be called on a virtual method.
              Because of this, the CLR has to do a virtual table lookup. There is some
              overhead in doing this. If a class is sealed, then it may be possible to
              avoid this. Something like this.

              ParentOfSealedC lass p = new ParentOfSealedC lass();
              p.SomeVirtualMe thod();
              SealedClass s = new ParentOfSealedC lass();
              s.SomeVirtualMe thod();

              In this case, when p.SomeVirtualMe thod(), it is possible that p could be a
              subclass of ParentOfSealedC lass and the method call cannot be optimized. But
              s.SomeVirtualMe thod() can be optimized. SealedClass cannot have children.
              The exact methods that are called on an instance of SealedClass are known at
              compile time. Because of this, s.SomeVirtualMe thod() will be a little faster.

              Also keep in mind that you can seal just a method or property in a class.
              This will do exactly the same kind of thing, just on a method or property
              basis.


              "Adrian <" wrote:
              When classes are not being inherited from. Is there an advantage to be
              gained by making them "sealed", and, if so, what is that advantage?
              >
              Thank you,
              Adrian.
              >
              >
              >

                Comment

                • ssamuel
                  #5
                  Re: Seald classes

                  Adrian,

                  Aside from the technical and performance benefits, it prevents
                  inheritance. If you're distributing a binary package to customers, you
                  can use sealed to make sure that they can't tamper with things that
                  should be untouched.


                  Stephan


                  Adrian < wrote:
                  When classes are not being inherited from. Is there an advantage to be
                  gained by making them "sealed", and, if so, what is that advantage?
                  >
                  Thank you,
                  Adrian.

                    Comment

                    • > Adrian
                      #6
                      Re: Seald classes

                      "Jeroen" <mercuros@gmail .comwrote in message
                      news:1163761244 .084594.323030@ b28g2000cwb.goo glegroups.com.. .
                      <snipped you seal classes to make sure nothing inherits from it, not
                      that you seal
                      classes that are not inherited from.
                      >
                      -Jeroen
                      "Ciaran O''Donnell" <CiaranODonnell @discussions.mi crosoft.comwrot e in
                      message news:C5D36332-058A-412D-BF42-400C92193F09@mi crosoft.com...
                      There could be a performance advantage <snipped>
                      Ciaran O'Donnell
                      "Bryan" <Bryan@discussi ons.microsoft.c omwrote in message
                      news:05F1F682-657F-4EE6-96B6-0239C55D97A7@mi crosoft.com...
                      It simplifies the virtual method table <snipped>
                      "ssamuel" <ssamuel@gmail. comwrote in message
                      news:1163778968 .739305.252970@ f16g2000cwb.goo glegroups.com.. .
                      Adrian,
                      >
                      <snippedyou can use sealed to make sure that they can't tamper with
                      things that
                      should be untouched.
                      >
                      Stephan
                      *************** *************** *********
                      M a n y t h a n k s,
                      Adrian



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