C Array Of Pointers

Question

In C   if I want an array of pointers so that I may have them point to different objects at a latter stage what does the syntax look like   EDIT  I need to clarify what I am trying to do I guess  I have a class foo that has and add method  In the add method I take a reference to class bar  I want to save that reference into a pointer array of bar  The array of pointer bar will need to be expanded all the time this I have no problems with  It is creating and array on the heap of pointers so that I may assign bar objects to them later  What I have tried seems to fail as class bar does not have a default constructor which the compiler is complaining about  This lead me to think that I was creating and array of actual objects which I did not want to do   Please no stl and no I do not want to hear about how you think this is crazy etc that is your opinion

User · Answer

I would do it something along these lines:

class Foo{
...
};

int main(){
  Foo* arrayOfFoo[100]; //[1]

  arrayOfFoo[0] = new Foo; //[2]
}

[1] This makes an array of 100 pointers to Foo-objects. But no Foo-objects are actually created.

[2] This is one possible way to instantiate an object, and at the same time save a pointer to this object in the first position of your array.

User · Answer

If you don t use the STL  then the code looks a lot bit like C    include  lt cstdlib gt   include  lt new gt   template lt  class T  gt  void append to array  T   amp arr  size t  amp n  T const  amp obj         T  tmp   static cast lt T  gt   std  realloc  arr  sizeof T     n 1           if   tmp    NULL   throw std  bad alloc    FUNCTION                assign things now that there is no exception     arr   tmp      new   amp arr  n     T  obj       placement new        n      T can be any POD type  including pointers   Note that arr must be allocated by malloc  not new

User · Answer

What you want is   Foo  array 10      array of 10 Foo pointers   Not to be confused with   Foo   array  10      pointer to array of 10 Foos   In either case  nothing will be automatically initialized because these represent pointers to Foos that have yet to be assigned to something  e g  with new    I finally  got  pointer array declaration syntax in C when I realized that it describes how you access the base type   Foo  array 5  10   means that  array 0  4  0  9   subscript on an array of 5 items  then subscript on an array of 10 items  then dereference as a pointer  will access a Foo object  note that    has higher precedence than      This seems backwards   You would think that int array 5  10    a k a  int  array 5   10    is an array of 10 int array 5    Suppose this were the case   Then you would access the last element of the array by saying array 9  4    Doesn t that look backwards too   Because a C array declaration is a pattern indicating how to get to the base type  rather than a composition of array expressions like one might expect   array declarations and code using arrays don t have to be flipflopped

User · Answer

boost ptr array  http   www boost org doc libs 1 43 0 libs ptr container doc ptr array html

User · Answer

For example  if you want an array of int pointers it will be int  a 10   It means that variable a is a collection of 10 int  s   EDIT  I guess this is what you want to do   class Bar       class Foo   public         Takes number of bar elements in the pointer array     Foo int size in         Foo        void add Bar amp  bar   private         Pointer to bar array     Bar   m pBarArr         Current fee bar index     int m index      Foo  Foo int size in    m index 0          Allocate memory for the array of bar pointers     m pBarArr   new Bar  size in      Foo   Foo           Notice delete   and not delete     delete   m pBarArr      m pBarArr   NULL     void Foo  add Bar  amp bar          Store the pointer into the array         This is dangerous  you are assuming that bar object       is valid even when you try to use it     m pBarArr m index       amp bar

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