Initializing a private array c++ - c++

Question

SOLVED! (See Edit)
I am trying to initialize an couple of arrays that are private members of a class. I am trying to use a public function to initialize these private arrays. My code looks like this:
void AP_PitchController::initGains(void){
_fvelArray[] = {20, 25, 30, 60, 90, 130, 160, 190, 220, 250, 280};
_kpgArray[] = {6.0, 6.0, 8.0, 4.0, 3.0, 2.5, 2.5, 2.5, 2.5, 2.5, 2.5};
_kdgArray[] = {2000, 2000, 1900, 300, 300, 200, 200, 200, 200, 200, 200};
_kigArray[] = {0.1, 0.1, 0.2, 0.25, 0.3, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5};
}
These arrays are found in the header file AP_PitchController where they are declared private. When I try to compile the code, I get one of these messages for each initialization:
/../AP_PitchController.cpp:106: error: expected primary-expression before ']' token
/../AP_PitchController.cpp:106: error: expected primary-expression before '{' token
/../AP_PitchController.cpp:106: error: expected `;' before '{' token
And here are my private declarations:
Private:
uint8_t _fvelArray[];
float _kpgArray[];
float _kdgArray[];
float _kigArray[];
Does anyone know what I am doing wrong to initialize these arrays upon the call of initGains()?
EDIT:
I found the answer in one of the related questions.
All i need to do is provide an array size for the initialization:
static float _kpgArray[11];
And then initialize it outside of a function in the .cpp file:
uint8_t AP_PitchController::_fvelArray[11] = {20, 25, 30, 60, 90, 130, 160, 190, 220, 250, 280};
Thank you for your input!

Answer 1

You can only use initialization syntax at declaration:
float _array[2] = {0.1f, 0.2f};
After it is declared you will have to initialize the members individually:
_array[0] = 0.1f;
_array[1] = 0.2f;
Or you could do it in a loop:
float temp[2] = {0.1f, 0.2f};
for( int i = 0; i < 2; ++i )
_array[i] = temp[i];

Answer 2

First, you cannot use the the initialization-list syntax that you're using since you've already declared your arrays (e.g. uint8_t _fvelArray = { ... }; would be valid when you first declare it under private: but _fvelArray = { ... }; is not valid in your initGains method). You must also declare the size of each array in your private declarations:
private:
uint8_t _fvelArray[10]; // or whatever size you want
Once you've taken those steps, you can populate the arrays:
_fvelArray[0] = 20;
_fvelArray[1] = 25;
// ...
Is there a reason you don't initialize your arrays right away? Will the gain values change? Your method is called initGains after all. If not, use the initializer-list syntax at the point of declaration:
private:
uint8_t _fvelArray[] = {20, 25, 30, 60, 90, 130, 160, 190, 220, 250, 280};

Answer 3

You have several issues here:
uint8_t _fvelArray[]; does not declare an array, but a pointer, the same as uint8_t *_fvelArray;. If you want to declare fixed-size array, you need to write uint8_t _fvelArray[11]; or in c++11 std::array<uint8_t, 11> _fvelArray;. For variable-length array you should use std::vector<uint8_t> _fvelArray;.
{20, ...} expression is an initializer-list an cannot be used for array initialization outside of its definition. That means that you can write uint8_t _fvelArray_tmp[] = {20, ...}; and then copy it to your variable : memcpy (_fvelArray, _fvelArray_tmp, sizeof (_fvelArray_tmp)); but not to initialize some already existing variable. But if you use std::array or std::vector for _fvelArray type, you could simply write _fvelArray = {20, ...}; (but it only works for c++11).