如何初始化指向指针数组的指针？

Question

I am trying to initialize a pointer to an array of pointers. Here's an example:

class MyClass { };

// INTENT: define a pointer to an array of pointers to MyClass objects
MyClass* (*myPointer)[];

int main(void) {

  // INTENT: define and initialize an array of pointers to MyClass objects
  MyClass * tempArray [] = {
    new MyClass(),
    new MyClass()
  };

  // INTENT: make myPointer point to the array just created
  myPointer = tempArray;

}

When I compile this I get:

./test2.cpp: In function ‘int main()’:
./test2.cpp:15:19: error: cannot convert ‘MyClass* [2]’ to ‘MyClass* (*)[]’ in assignment
   myPointer = tempArray;
               ^~~~~~~~~

Answer 1

First, arrays are not pointers. You have to use the address-of:

 myPointer = &tempArray;

Next, when you write

T foo[] = { t1, t2 };

this is just short-hand notation for

T foo[2] = { t1, t2 };

Either use the correct type ( Live Example ):

MyClass* (*myPointer)[2];

or perhaps better use a std::array<MyClass> in the first place. And forget about raw owning pointers. Use smart pointers instead.

Answer 2

// INTENT: define a pointer to an array of pointers to MyClass objects
MyClass* (*myPointer)[];

You can't obmit the size of the array in declaration. You need this:

MyClass* (*myPointer)[2];

Then,

  MyClass * tempArray [] = {
    new MyClass(),
    new MyClass()
  };

  // INTENT: make myPointer point to the array just created 
  myPointer = &tempArray;

Answer 3

An array decays into a pointer to the first element. Since the element type is also a pointer, you can declare a variable that is a double-pointer and have it point at that element, eg:

class MyClass { };

MyClass** myPointer;

int main(void) {

  MyClass * tempArray [] = {
    new MyClass(),
    new MyClass()
  };

  myPointer = tempArray;
    // same as:
    // myPointer = &tempArray[0];

  ...
}