Databases
StackOverflow2013
Postsdbo
PODerived class implementing multiple interfaces with a common function signature
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PODerived class implementing multiple interfaces with a common function signature
    primarykey
    data
    text
    <p>I'm getting a compile error when I try to compile my code. The error is this:</p> <pre><code>multi.cc: In function ‘int main()’: multi.cc:35: error: cannot declare variable ‘mdc’ to be of abstract type ‘MostDerivedClass’ multi.cc:27: note: because the following virtual functions are pure within ‘MostDerivedClass’: multi.cc:13: note: virtual int Interface2::common_func() multi.cc:36: error: request for member ‘common_func’ is ambiguous multi.cc:13: error: candidates are: virtual int Interface2::common_func() multi.cc:21: error: virtual int InterimClass::common_func() </code></pre> <p>And here is my code:</p> <pre><code>class Interface1 { public: virtual int common_func() = 0; virtual ~Interface1() {}; }; class Interface2 { public: virtual int common_func() = 0; virtual int new_func() = 0; virtual ~Interface2() {}; }; class InterimClass : public Interface1 { public: virtual int common_func() { return 10; } }; class MostDerivedClass : public InterimClass, public Interface2 { public: virtual int new_func() { return 20; } }; int main() { MostDerivedClass mdc; int x = mdc.common_func(); cout &lt;&lt; "The value = " &lt;&lt; x &lt;&lt; endl; Interface2 &amp;subset_of_funcs = dynamic_cast&lt;Interface2 &amp;&gt;(mdc); x = subset_of_funcs.common_func(); } </code></pre> <p>My questions:</p> <ul> <li><p>How do I tell the compiler that common_func() is already implemented by the InterimClass which is a base class of MostDerivedClass?</p></li> <li><p>Is there another way to fix my problem? What I would really like to do is to be able to also call common_func from Interface2. I'm working with some legacy code with a huge amount of methods in Interface1. In my new code, I only want to call a small set of these Interface1 functions, plus a few that I need to add.</p></li> </ul>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. UShopia
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PODerived class implementing multiple interfaces with a common function signature
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PODerived class implementing multiple interfaces with a common function signature
      1. This table or related slice is empty.
      1. VTUpMod
    1. COYour common function is not actually 'common'. `Interface1::common_func()` has nothing common with `Interface2::common_func()`. If you want actually common function, you should derive `Interface2` from `Interface1`. And then apply @juanchopanza answer.
      singulars
      1. PODerived class implementing multiple interfaces with a common function signature
      1. USLol4t0
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload