数组初始化，初始化器值太多

Question

I am defining a member variable like this:

float m_Colors[4];

In the constructor I want to initialize it like this:

m_Color = {0.0f, 0.0f, 0.0f, 1.0f};

Even though I have done this a million times before on this particular occasion I get the error "too many initializer values". How could on these two very simple lines of code possibly be something wrong? Please englighten me.

Answer 1

You cannot reinitialize the array again with the initializer syntax (it was already default initialized when the class was constructed).

You can use the use a ctor initializer list to initialize the array when the class is constructed.

struct S 
{
    S( ) 
      :  floats_{ 1.0f, 2.2f, 3.3f, 4.4f } 
    {  }

private:
    float floats_[ 4 ];
};

Answer 2

If you want use initializer for built in array, you must do when declare it. Otherwise you can use like this in your constructor:

float tmp[] = { 0.0f, 0.0f, 0.0f, 1.0f };
memcpy_s(m_Colors, 4, tmp, 4);

Answer 3

You can use std::array<...> as datatype for your member. This way you can initialise it with curly-braces and also assign it this way if needed plus you get some additional modern C++ benefits.

#include <array>

class Object
{
public:
    Object() : m_Colors{0.0f, 0.0f, 0.0f, 1.0f}
    {
    }

private:
    std::array<float, 4> m_Colors;
};

If you need to reassign:

void reinit()
{
    m_Colors = {0.0f, 0.0f, 0.0f, 1.0f};
}