"Excess elements in scalar initializer" error in 2d array

Question

I need to use 2 dimension array in my game so;

First I'M declaring it like this in my header file called "HelloWorldScene.h":

using namespace cocos2d;

class HelloWorld : public Layer
{
    private:
    ...
    int upgradeCosts[4][4];
    ...
}

Then I'm tryin to define it in my source file called "HelloWorldScene.cpp":

#include "HelloWorldScene.h"
...
bool HelloWorld::init()
{
....
upgradeCosts[4][4] = {{150, 250, 900, 1800},
                      {100, 200, 600, 1200},
                      {200, 350, 1200, 2000},
                      {150, 300, 1000, 1900}};
...
}

But it gives me this error: "Excess elements in scalar initializer"

The entire code between brackets {{150, ...... , 1900 }} are underlined with red. And i dont know what to do, please help me.

With almost 100 rep, I expect better search for duplicate questions next time. :) — gsamaras, Jul 17 '18 at 14:45
See also [How to initialize an array member](https://stackoverflow.com/questions/4810664/how-do-i-use-arrays-in-c/4984228#4984228). — Raymond Chen, Jul 17 '18 at 14:45

score 4 · Accepted Answer · edited Jul 17 '18 at 15:59

This is absolutely wrong to initialize the whole array like this :

upgradeCosts[4][4] = {{150, 250, 900, 1800},
                      {100, 200, 600, 1200},
                      {200, 350, 1200, 2000},
                      {150, 300, 1000, 1900}};

Because you just set the [4][4] element, not the whole array. This what the Excess elements in scalar initializer error refers to. An int is a scalar, it can only be initialised with 1 value, yet you attempt to initialise it with 16 values.

To correct this you would assume you could do this:

bool HelloWorld::init()
{
    upgradeCosts = {{150, 250, 900, 1800},
                    {100, 200, 600, 1200},
                    {200, 350, 1200, 2000},
                    {150, 300, 1000, 1900}};
}

However this will not work because upgradeCosts has already been default initialised during the construction of HelloWorld and cannot be initialised again.

A naive solution to this would be like the following:

bool HelloWorld::init()
{
    int data[4][4] = {{150, 250, 900, 1800},
                      {100, 200, 600, 1200},
                      {200, 350, 1200, 2000},
                      {150, 300, 1000, 1900}};

    for(int i = 0;i < 3;i++)
        for(int j = 0;j < 3;j++)
            upgradeCosts[i][j] = data[i][j];
    ...
}

However, this involves pointless copying. A better solution would be to move the array initialisation out of the init method altogether. You can do this by either just initialising the array in the header file:

// hpp file
class HelloWorld
{
    private:
    int upgradeCosts[4][4] = {{150, 250, 900, 1800},
                              {100, 200, 600, 1200},
                              {200, 350, 1200, 2000},
                              {150, 300, 1000, 1900}};

    public:
    bool init();
};

Or you could initialise it in the constructor of HelloWorld:

// hpp file
class HelloWorld
{
    private:
    int upgradeCosts[4][4];

    public:
    HelloWorld();
    bool init();
};

// cpp file
HelloWorld::HelloWorld()
    : upgradeCosts{{150, 250, 900, 1800},
                   {100, 200, 600, 1200},
                   {200, 350, 1200, 2000},
                   {150, 300, 1000, 1900}}
{ }

Or if you know that your upgradeCosts should be the same across all instances of HelloWorld you can use a static member and initialise it like below :

// hpp file
class HelloWorld
{
    private:
    const static int upgradeCosts[4][4];

    public:
    bool init();
};

// cpp file
const int HelloWorld::upgradeCosts[4][4] = {{150, 250, 900, 1800},
                                            {100, 200, 600, 1200},
                                            {200, 350, 1200, 2000},
                                            {150, 300, 1000, 1900}};

If I had to come up with a 'worst solution' this would be it. Why on earth wouldn't you use a constructor or initialise the array in the header or (probably more correctly in this use case) mark the array static and initialise in the cpp file? — Fibbs, Jul 17 '18 at 15:02
@Fibbles of course `static` member is another solution, so i add it to my answer. — BattleTested_закалённый в бою, Jul 17 '18 at 15:17
I have made some edits to your answer to reflect that an `init` method is not a very C++ way of doing things. I have also included constructor initialisation which would be the most common solution to this problem. — Fibbs, Jul 17 '18 at 15:35

"Excess elements in scalar initializer" error in 2d array

1 Answers1