我正在試圖創建一個指向類對象的void指針,並在函數內初始化它。不幸的是,類的數組成員不能轉義該函數,即它在初始化後不能被訪問。Void指向類對象的指針:函數內部的初始化
在下面的代碼中,第一次調用打印位置(在初始化函數內部)可以正常工作,但是,第二次調用從初始化函數外部打印位置失敗。我有一種感覺,在初始化函數中創建的數組對象被銷燬並且不會傳遞,但我不確定,也不知道如何解決它。
任何幫助將不勝感激。
#include <iostream>
#include <iomanip>
#include <string>
class Atoms
{
double * positions;
int nAtoms;
public:
// Standard constructor prividing a pre-existant array
Atoms(int nAtoms, double * positionsArray)
{
this->nAtoms = nAtoms;
this->positions = positionsArray;
}
// Print positions to screen
void print_positions()
{
std::cout<< "nAtoms: " << this->nAtoms << std::endl;
int nDim = 3;
for (int i = 0; i < nAtoms; i++)
{
for (int j = 0; j < nDim; j++)
{
std::cout << std::setw(6) << this->positions[i * nDim + j] << " ";
}
std::cout << std::endl;
}
std::cout << std::endl;
}
};
void initialize_Atoms_void_pointer(void ** voidAtomsPointer)
{
//Create a new instance of Atoms by a pointer
int numAtoms = 5;
int numDim = 3;
int elemN = numAtoms * numDim;
double data_array[elemN];
for (int i = 0; i < numAtoms; i++)
for (int j = 0; j < numDim; j++)
{
data_array[i * numDim + j] = i * numDim + j + 10;
}
Atoms *atoms = new Atoms(numAtoms, data_array);
// Set the vPointer that the void pointer points to a pointer to Atoms object
*voidAtomsPointer = static_cast<void *>(atoms);
//Test call
std::cout << std::endl << "Initializing atoms" << std::endl;
static_cast<Atoms *>(*voidAtomsPointer)->print_positions();
}
void print_Atoms_pointer_positions(void * voidAtomsPointer)
{
//Cast the pointer as an atoms pointer
Atoms *atomsPointer = static_cast<Atoms *>(voidAtomsPointer);
atomsPointer->print_positions();
}
int main()
{
//Use the initializer function for getting a pointer
void *testVoidAtomsPointer;
initialize_Atoms_void_pointer(&testVoidAtomsPointer);
print_Atoms_pointer_positions(testVoidAtomsPointer);
}
除了作爲本地核心問題的數組之外,另一個問題是'elemN'不是一個編譯時常量表達式,所以將它用作數組大小是不合適的。這很容易通過添加'const'來解決。 – user2079303
'new','void *'。即使C++ 98有'std :: vector',C++ 11也引入了'std :: shared_ptr <>'。這段代碼真的很痛苦,因爲它重新發明了輪子,很糟糕。 – MSalters
感謝您的建議。不幸的是,在這個問題中,我受到限制只能使用非常基本的工具。 –