C++ - Error: expected unqualified-id before ‘using’ - c++

Question

I have a C++ program and when I try to compile it it gives an error:
calor.h|6|error: expected unqualified-id before ‘using’|
Here's the header file for the calor class:
#ifndef _CALOR_
#define _CALOR_
#include "gradiente.h"
using namespace std;
class Calor : public Gradiente
{
public:
Calor();
Calor(int a);
~Calor();
int getTemp();
int getMinTemp();
void setTemp(int a);
void setMinTemp(int a);
void mostraSensor();
};
#endif
Why does this happen?
This class inherits from gradiente:
#ifndef _GRADIENTE_
#define _GRADIENTE_
#include "sensor.h"
using namespace std;
class Gradiente : public Sensor
{
protected:
int vActual, vMin;
public:
Gradiente();
~Gradiente();
}
#endif
Which in turn inherits from sensor
#ifndef _SENSOR_
#define _SENSOR_
#include <iostream>
#include <fstream>
#include <string>
#include "definicoes.h"
using namespace std;
class Sensor
{
protected:
int tipo;
int IDsensor;
bool estadoAlerta;
bool estadoActivo;
static int numSensores;
public:
Sensor(/*PARAMETROS*/);
Sensor(ifstream &);
~Sensor();
int getIDsensor();
bool getEstadoAlerta();
bool getEstadoActivo();
void setEstadoAlerta(int a);
void setEstadoActivo(int a);
virtual void guardaSensor(ofstream &);
virtual void mostraSensor();
// FUNÇÃO COMUM
/* virtual int funcaoComum() = 0;
virtual int funcaoComum(){return 0;};*/
};
#endif
For completeness' sake, here's definicoes.h
#ifndef _DEFINICOES_
#define _DEFINICOES_
const unsigned int SENSOR_MOVIMENTO = 0;
const unsigned int SENSOR_SOM = 1;
const unsigned int SENSOR_PRESSAO = 2;
const unsigned int SENSOR_CALOR = 3;
const unsigned int SENSOR_CONTACTO = 4;
const unsigned int MIN_MOVIMENTO = 10;
const unsigned int MIN_SOM = 10;
const unsigned int MIN_PRESSAO = 10;
const unsigned int MIN_CALOR = 35;
#endif
What am I doing wrong?

Answer 1

There is a semicolon missing at the end of this class:
class Gradiente : public Sensor
{
protected:
int vActual, vMin;
public:
Gradiente();
~Gradiente();
} // <-- semicolon needed after the right curly brace.
Also, the names of your include guards are illegal. Names that begin with an underscore and an uppercase letter are reserved for the C++ implementation (as are names containing a double underscore) - you are not allowed to create such names in your own code. And you should never use:
using namespace std;
in a header file. And lastly, the destructor in your Sensor base class should almost certainly be made virtual.

Answer 2

In gradiente.h you forgot the semicolon at the end of your class declaration.
You need this:
class Gradiente : public Sensor
{
protected:
int vActual, vMin;
public:
Gradiente();
~Gradiente();
};
See the added semicolon?

Answer 3

You forgot to leave the last semi colon on the closing brackets, };, on the gradiente class.