Declare Array in Class and Initialize it in Constructor

Question

I have the following problem:

I have a class in a header file where I want to declare a two-dimensional array (map).

Then I want to initialize it in the Constructor in the Source-File (cpp) File.

Till now this looks like this:

Headerfile:

class TForm1 : public TForm
{
private:    ...
public:
    __fastcall TForm1(TComponent* Owner);
    int map[][];
};

Sourcefile:

__fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) {

map[][] = { {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
{ 1, 2, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 2, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1 },
{ 1, 7, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 7, 1 },
{ 1, 0, 1, 0, 1, 1, 1, 3, 1, 1, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 3, 3, 3, 3, 3, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 3, 12, 3, 13, 3, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 3, 3, 14, 3, 3, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1 },
{ 1, 0, 0, 2, 0, 0, 0, 5, 0, 0, 0, 2, 0, 0, 1 },
{ 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 3, 1, 0, 1, 3, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1 },
{ 1, 0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 1 },
{ 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1 },
{ 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1 },
{ 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1 },
{ 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1 },
{ 1, 2, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 2, 1 },
{ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 }
};

}

I know this is terribly wrong but I couldnt find any helpful explaination in the internet how it should be done correctly.

Thanks for you help

Answer 1

It is not pretty and flexible. May be you should use Abstract Factory Pattern to do this. And i think you can use std::vector instead of multidimensional arrays. It has many advantages and STL library has reach algorithms to handle with std::vector . For example:

class IMapInitializer
{
public:
    virtual void InitMap(std::vector<std::vector<int>>& map) = 0;
    virtual ~IMapInitializer(){}
};

class HardcordeMapInitializer : public IMapInitializer
{
public:
    virtual void InitMap(std::vector<std::vector<int>>& map) override
    {
        map = {{1,2,3},{1,2,3},{1,2,3}};
    }
};

class FileMapInitializer : public IMapInitializer
{
public:
    virtual void InitMap(std::vector<std::vector<int>>& map) override
    {
        //Read map from file
    }
};

//...
class TForm1 : public TForm
{
private:    ...
public:
    __fastcall TForm1(TComponent* Owner, IMapInitializer& mapInitializer );
    std::vector<std::vector<int>> map;
};

//...
__fastcall TForm1::TForm1(TComponent* Owner, IMapInitializer& mapInitializer ) : TForm(Owner) {

mapInitializer.InitMap(map);

With a help of this pattern you can choose better way to init map and change it in process of development.

In my example I showed 2 factories(hardcode and fileInput) you can think some others later and use.

Answer 2

C++ does not allow to define an array with more than one indeterminate dimension; It is possible to write int[][15] = ... , but it is not legal to write int [][] = ... .

If all of your dimensions are dynamic, I'd suggest to use a vector of vectors. See the following program illustrating this:

class ClassWith2DArray {
public:
    ClassWith2DArray();
    vector<vector<int>> map;
};

ClassWith2DArray::ClassWith2DArray() : map ({{2,3},{3,4}}) {}


int main()
{
    ClassWith2DArray c;
    for (auto row : c.map) {
        for (auto column : row) {
            cout << column << " ";
        }
        cout << endl;
    }


    return 0;
}