Databases
StackOverflow2013
Postsdbo
POCalling overloaded constructor from constructor initialisation list
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POCalling overloaded constructor from constructor initialisation list
    primarykey
    data
    text
    <p>In the code below, my intent is to call one of two overloaded constructors for the <code>kap</code> (class <code>opacity</code>) based on what arguments are passed to the object of class <code>material</code>:</p> <pre><code>class opacity{ private: int mode; double kap_const; double kappa_array[10][10]; public: opacity(double constkap); // picking the constructor sets the mode opacity(char* Datafile); double value(double T, double P); // will return a constant or interpolate }; opacity::opacity(double constkap):mode(1){ kap_const = constkap; } opacity::opacity(char* Datafile):mode(2){ // read file into kappa_array... } class Matter { public: Matter(int i, double k, char* filename); // many more values are actually passed opacity kap; int x; // dummy thing // more variables, call some functions }; Matter::Matter(int i, double k, char * filename) :x(k&gt;0? this-&gt;kap(x): this-&gt;kap(filename) ) { // ... rest of initialisation } </code></pre> <p>This is however not working:</p> <pre><code>test.cpp: In constructor 'Matter::Matter(int, double, char*)': test.cpp:32:21: error: no match for call to '(opacity) (void*&amp;)' test.cpp:32:42: error: no match for call to '(opacity) (char*&amp;)' test.cpp:32:44: error: no matching function for call to 'opacity::opacity()' test.cpp:32:44: note: candidates are: test.cpp:20:1: note: opacity::opacity(char*) test.cpp:20:1: note: candidate expects 1 argument, 0 provided test.cpp:16:1: note: opacity::opacity(double) test.cpp:16:1: note: candidate expects 1 argument, 0 provided test.cpp:4:7: note: opacity::opacity(const opacity&amp;) test.cpp:4:7: note: candidate expects 1 argument, 0 provided </code></pre> <p>The first thing I had tried,</p> <pre><code>Matter::Matter(int i, double k, char * filename) :kap(k&gt;0? k: filename) { // use k&lt;0 as a flag to read from filename // ... rest of initialisation } </code></pre> <p>also failed, because "the result of a ternary operator always has to be the same type" for compile-time reasons, as pointed out in a <a href="https://stackoverflow.com/questions/4693629/ternary-operator?answertab=votes#tab-top">similar question</a> (although they were not explained there, it seems).</p> <p>Now, the inelegant solution would be to also overload the <code>Matter</code> constructor based on the arguments that the <code>kap</code> constructor should receive, but this is (1) very inelegant, especially since the <code>Matter</code> constructor takes many variables and performs many actions (so a lot of code would be duplicated just to vary the <code>kap</code> part of the constructor initialisation list), and (2) this can get out of hand if there is another class used with <code>Matter</code> that also has different constructors: for <em>M</em> classes with <em>N</em> c'tors, one ends up with <em>N</em>^ <em>M</em> combinations...</p> <p>Would someone have a suggestion or a work-around? Thanks in advance!</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCommunity
    1. USLabbedudl
    plurals
    1. PL
      singulars
      1. LTLinked
    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. This table or related slice is empty.
    1. COI think you have to add a special constructor to `opacity`. Either one that takes an int and filename, or a default constructor so you can assign it in the body of `Matter`s constructor.
      singulars
      1. POCalling overloaded constructor from constructor initialisation list
      1. USMooing Duck
    2. COWhy don't you pass the opacity kap as a constructor argument ? You can use the ternary operator before calling the constructor, then create an opacity object (on the heap probably) and pass a pointer to it in the matter constructor.
      singulars
      1. POCalling overloaded constructor from constructor initialisation list
      1. USJohn
    3. CO@MooingDuck Ah, did you mean what Johannes Schaub wrote? Thanks for your answer.
      singulars
      1. POCalling overloaded constructor from constructor initialisation list
      1. USLabbedudl
 

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