Declaring an object in header file - c++

Question

I created a class called coordinate
I want to create a vector of coordinate objects called cooPos to use it in another class called ScribbleArea. (It is from a Qt Example).
For some reason I always get the error:
error: cooPos was not declared in this scope
coordinates.h
#ifndef COORDINATE_H
#define COORDINATE_H
#include <iostream>
#include <string>
class coordinate
{
public:
coordinate(float y, float x, bool isPressed);
float get_x();
float get_y();
std::string get_coordinateText();
private:
float x_pos;
float y_pos;
bool isPressedState;
};
#endif // COORDINATE_H
coordinate.cpp
#include "coordinate.h"
coordinate::coordinate(float y, float x, bool isPressed)
{
y_pos = y;
x_pos = x;
isPressedState = isPressed;
}
std::string coordinate::get_coordinateText()
{
std::string output;
output = "X: " + std::to_string(x_pos) + " Y: " + std::to_string(y_pos) +"\n";
return output;
}
float coordinate::get_x()
{
return x_pos;
}
float coordinate::get_y()
{
return y_pos;
}
scribblearea.h
#ifndef SCRIBBLEAREA_H
#define SCRIBBLEAREA_H
#include <QColor>
#include <QImage>
#include <QPoint>
#include <QWidget>
#include <iostream>
#include <vector>
#include "coordinate.h"
class ScribbleArea : public QWidget
{
Q_OBJECT
public:
ScribbleArea(QWidget *parent = 0);
private:
void addCoordinate(float x, float y, bool isPressed);
std::vector<coordinate> cooPos;
};
#endif
scribbleare.cpp
#include <QtWidgets>
#ifndef QT_NO_PRINTER
#include <QPrinter>
#include <QPrintDialog>
#endif
#include "scribblearea.h"
ScribbleArea::ScribbleArea(QWidget *parent)
: QWidget(parent)
{
setAttribute(Qt::WA_StaticContents);
}
void addCoordinate(float x, float y, bool isPressed)
{
coordinate *actPos = new coordinate(y,x,isPressed);
cooPos.push_back(*actPos);
}
I have really no idea...