Im having the typical c error of "x" is not declared in this scope.
This is my main.cpp:
#include <iostream>
#include <cstdlib>
#include <cstring>
#include "funciones.h"
using namespace std;
class Materia{
private:
int nroMateria;
char nombreMateria[40];
int cantAlumnos;
int cantDocentes;
public:
void Cargar(){
int nro;
cout<<"NUMERO DE MATERIA: ";
cin>>nro;
setNroMateria(nro);
cout<<"NOMBRE DE MATERIA: ";
cin.ignore();
cin.getline(nombreMateria,35);
cout<<"CANTIDAD DE ALUMNOS: ";
cin>>cantAlumnos;
cout<<"CANTIDAD DE DOCENTES: ";
cin>>cantDocentes;
}
void Mostrar();
void setNroMateria(int nm){if(nm>0)nroMateria=nm;}
void setNombreMateria(const char *nm){strcpy(nombreMateria,nm);}
int getNroMateria(){return nroMateria;}
char *getNombreMateria(){return nombreMateria;}
};
void Materia::Mostrar(){
cout<<"NUMERO DE MATERIA: ";
cout<<nroMateria<<endl;
cout<<"NOMBRE DE MATERIA: ";
cout<<nombreMateria<<endl;
cout<<"CANTIDAD DE ALUMNOS: ";
cout<<cantAlumnos<<endl;
cout<<"CANTIDAD DE DOCENTES: ";
cout<<cantDocentes<<endl;
cout<<endl;
cout<<"-------------------------"<<endl;
cout<<endl;
}
int main(){
int opc;
while(true){
system("cls");
cout<<"MENU ARTICULOS: "<<endl;
cout<<"1. CARGAR MATERIAS: "<<endl;
cout<<"2. MOSTRAR MATERIAS: "<<endl;
cout<<"0. SALIR DEL PROGRAMA: "<<endl;
cout<<"SELECCIONE UNA OPCCION: "<<endl;
cin>>opc;
system("cls");
switch(opc){
case 1:
CargarMateria();
break;
case 2:
MostrarMateria();
break;
case 0:
return 0;
break;
}
system("pause");
}
return 0;
}
And i have my class Materia with all its properties and methods. And then i have a menu to trigger different options.
This is my funciones.h file:
void CargarMateria();
void MostrarMateria();
bool grabarEnDisco(Materia);
void CargarMateria(){
Materia obj;
obj.Cargar();
if(grabarEnDisco(obj)==true){
cout<<"REGISTRO AGREGADO";
}else {
cout<<"NO SE PUDO AGREGAR EL REGISTRO";
}
cout<<endl;
}
void MostrarMateria(){
FILE *pMateria;
Materia obj;
pMateria = fopen("materias.dat", "rb");
///wb abre el archivo en modo escritura -> SIEMPRE CREA UN ARCHIVO VACIO
///ab abre el archivo y permite que se le agreguen registros.
///rb abre el archivo y permite leer los registros. Si no existe da error.
if(pMateria == NULL){
cout<<"ERROR DE ARCHIVO";
return;
}
fread(&obj,sizeof(Materia),1,pMateria);
fclose(pMateria);
obj.Mostrar();
}
bool grabarEnDisco(Materia obj){
FILE *pMateria;
pMateria = fopen("materias.dat", "wb");
///wb abre el archivo en modo escritura -> SIEMPRE CREA UN ARCHIVO VACIO
///ab abre el archivo y permite que se le agreguen registros.
///rb abre el archivo y permite leer los registros. Si no existe da error.
if(pMateria == NULL){
cout<<"ERROR DE ARCHIVO";
return false;
}
fwrite(&obj,sizeof(Materia),1,pMateria);
fclose(pMateria);
return true;
}
#endif // FUNCIONES_H_INCLUDED
And above i have a few functions to generate write and read a file. But where i first have a prototype function:
bool grabarEnDisco(Materia);
I get
'Materia' was not declared in this scope
Any clue way this is happening?
CodePudding user response：
Your functions header file is included before you defined Materia. Therefore, when the compiler starts compiling your main, it sees a function that takes a parameter of some undefined type, and tells you that this type hasn't been declared yet.
You can either move the include to be below the class definition, place a forward declaration of the class before the functiones.h include, or, my personal recommendation, move the Materia class into its own header file and include that from main and functiones.h.
CodePudding user response：
Based on @alex`s answer Your functions header file is included before you defined Matter, so you can use everything in one file, example Matter.cpp as in the following example
or simply by declaring Materia class inside funciones.h like this:
using namespace std;
class Materia{
private:
int nroMateria;
char nombreMateria[40];
int cantAlumnos;
int cantDocentes;
public:
void Cargar(){
int nro;
cout<<"NUMERO DE MATERIA: ";
cin>>nro;
setNroMateria(nro);
cout<<"NOMBRE DE MATERIA: ";
cin.ignore();
cin.getline(nombreMateria,35);
cout<<"CANTIDAD DE ALUMNOS: ";
cin>>cantAlumnos;
cout<<"CANTIDAD DE DOCENTES: ";
cin>>cantDocentes;
}
void Mostrar();
void setNroMateria(int nm){if(nm>0)nroMateria=nm;}
void setNombreMateria(const char *nm){strcpy(nombreMateria,nm);}
int getNroMateria(){return nroMateria;}
char *getNombreMateria(){return nombreMateria;}
};
void Materia::Mostrar(){
cout<<"NUMERO DE MATERIA: ";
cout<<nroMateria<<endl;
cout<<"NOMBRE DE MATERIA: ";
cout<<nombreMateria<<endl;
cout<<"CANTIDAD DE ALUMNOS: ";
cout<<cantAlumnos<<endl;
cout<<"CANTIDAD DE DOCENTES: ";
cout<<cantDocentes<<endl;
cout<<endl;
cout<<"-------------------------"<<endl;
cout<<endl;
}
void CargarMateria();
void MostrarMateria();
bool grabarEnDisco(Materia);
void CargarMateria(){
Materia obj;
obj.Cargar();
if(grabarEnDisco(obj)==true){
cout<<"REGISTRO AGREGADO";
}else {
cout<<"NO SE PUDO AGREGAR EL REGISTRO";
}
cout<<endl;
}
void MostrarMateria(){
FILE *pMateria;
Materia obj;
pMateria = fopen("materias.dat", "rb");
///wb abre el archivo en modo escritura -> SIEMPRE CREA UN ARCHIVO VACIO
///ab abre el archivo y permite que se le agreguen registros.
///rb abre el archivo y permite leer los registros. Si no existe da error.
if(pMateria == NULL){
cout<<"ERROR DE ARCHIVO";
return;
}
fread(&obj,sizeof(Materia),1,pMateria);
fclose(pMateria);
obj.Mostrar();
}
bool grabarEnDisco(Materia obj){
FILE *pMateria;
pMateria = fopen("materias.dat", "wb");
///wb abre el archivo en modo escritura -> SIEMPRE CREA UN ARCHIVO VACIO
///ab abre el archivo y permite que se le agreguen registros.
///rb abre el archivo y permite leer los registros. Si no existe da error.
if(pMateria == NULL){
cout<<"ERROR DE ARCHIVO";
return false;
}
fwrite(&obj,sizeof(Materia),1,pMateria);
fclose(pMateria);
return true;
}
#endif // FUNCIONES_H_INCLUDED
CodePudding user response：
Let me elaborate on what Alex said.
The contents of functiones.h appears to be a CPP file, and should not be a header file. For this simple program, that would typically go in the same file as the main. For a project, that should be functions.cpp (remove the #ifdef guard) and make a separate functiones.h that contains just the declarations of the functions that will be called from the main program.
Your program should look like this:
main.cpp
#include <iostream>
#include <cstdlib>
#include <cstring>
#include "materia.h"
#include "funciones.h"
int main()
{
⋮
}
functiones.h
void CargarMateria();
void MostrarMateria();
functiones.cpp
#include < any needed system files >
#include "materia.h"
#include "functiones.h" // always include "my own" header too.
// All the functions you defined in the original functiones.h
materia.h
#pragma once
#ifdef SOME_UUID_THAT_WILL_BE_GLOBALLY_UNIQUE
#define that same thing
#include < any needed system files >
class Materia
{
⋮
};
#endif
In addition, you have one member function of class Materia that is not defined inside the class body. That needs to go into a materia.cpp file, or if you put it in the header file (still outside the class body) you need to use the inline keyword.
meanwhile...
Don’t write using namespace std;.
You can, however, in a CPP file (not H file) or inside a function put individual using std::string; etc. (See SF.7.)
⧺SL.io.50 Don't use endl.
Prefer using the C library features rather than the old C library. You're using FILE* stuff, but you also use cin and cout in your program. Really really don't use strcpy and similar, or pass around const char* for strings.
Don't use the C macro for NULL. C has a proper typed nullptr. But, don't directly compare pointers against nullptr; rather, use the truth value directly.
if(pMateria == NULL) should be if(pMateria). But if you were using fstream rather than FILE* you would not be doing that anyway.
The style in C is to put the * or & with the type, not the identifier. This is called out specifically near the beginning of Stroustrup’s first book, and is an intentional difference from C style.