Thread: Am I using *this properly?

I have already written a calculator engine that works equally well in both windows and console mode due to it's IO de-coupled design.

My goal now is to extend that functionality to a Calculator class along with it's more generic helper classes. The class I am working on now is the StringList class which will track and traverse a list of user input strings.

Here is where i am unsure. The polymorphic constructor StringList() in one instance will add the StringList object at hand to the single argument, StringList *head. So I am returning *this, but how?

Code:

class StringList
{

  StringList *next;

  char *string;

  StringList *prev;
     

StringList * StringList::StringList(int thisManyChars)
 {   next = NULL; string = NewString(thisManyChars);                                                    prev = NULL;  return *this;}

StringList * StringList::StringList(StringList *head, thisManyChars)
  {  string = NewString(thisManyChars);
      StringNode *t = head; while(t->next != NULL) t = t->next;
      prev = t; t->next = this; next = NULL;  return *this;}
 
StringList * StringList::StringList(StringList *head)
  {  string = NewString(100);
      StringNode *t = head; while(t->next != NULL) t = t->next;
      prev = t; t->next = this; next = NULL;  return *this;}

StringList * StringList::StringList()
                 {next = NULL; string = NewString(100);
                   prev = NULL;  return *this;}



  StringList::~StringList(){ free(string); }
};

Am I using *this properly?

IMO, no. The this pointer refers to the object at hand. In your code in the following line:

t->next = this;

the this pointer appears to be refering to the variable called string whcih is of type char *, whereas the object at hand is of type StringList as eviedenced by the function definition:

StringList * StringList::StringList(StringList *head, thisManyChars)


Likewise the above definition indicates that the return type will be of type pointer to StringList, but the following line returns a deferenced pointer, rather than the pointer per se.

return *this;

Thanks.