Vector of struct in C

Question

I can’t find the error in this code of mine of an exercise. It prints right the first reading, then prints random things. I could not find out if the error is in the reading or in the print.

#include <stdio.h>
#include <stdlib.h>
/*Defina uma estrutura que irá representar bandas de música.
Essa estrutura deve ter o nome da banda, que tipo de música ela toca,
 o número de integrantes e em que posição do ranking essa banda está dentre as suas 5 bandas favoritas.*/
#define TAM 2

 typedef struct
 {
     char nome[20],tipo[15];
     int integrantes,posicao;
 }BANDAS[TAM];

int main()
{

    BANDAS banda[TAM];
    ler (&banda);

    mostrar(banda);


    return 0;
}

void ler (BANDAS *banda)
{
    int i;

    for (i=0;i<TAM;i++){
        printf ("Diga qual o nome da banda: ");
        gets(banda[i]->nome);
    __fpurge(stdin);

        printf ("Tipo de musica: ");
        gets (banda[i]->tipo);
    __fpurge (stdin);

        printf ("Quantos integrantes tem a banda: ");
        scanf ("%d",&banda[i]->integrantes);
     __fpurge (stdin);
        printf ("Posicao no seu top 5: ");
        scanf ("%d",&banda[i]->posicao);
        __fpurge (stdin);
    }
}

void mostrar (BANDAS banda)
{
    int i;
    for (i=0;i<TAM;i++){

    printf ("Nome: %s\n",banda[i].nome);
    printf ("Tipo de musica: %s\n",banda[i].tipo);
    printf ("Numero de integrantes: %d \n",banda[i].integrantes);
    printf ("Posicao no seu TOP 5: %d \n",banda[i].posicao);
    }

}

Am I iterating wrong in reading? How would be right ?

Answer 1

I believe the biggest problem in the program is the declaration:

typedef struct
{
    char nome[20],tipo[15];
    int integrantes,posicao;
} BANDAS[TAM];

In this statement, you are creating a guy array, with TAM positions.

And in function main(), when you declare:

BANDAS banda[TAM];

In fact, he’s creating a matrix, since the typedef already defines a array.

The translation of this instruction by the compiler would look something like this (example):

struct BANDAS banda[2][2];

and probably, that’s not what you want the show to do.

---

If you really intend to create the guy BANDAS as array, the solution is to change the variable declaration banda in main to:

BANDAS banda;

and in function ler(), change the references to array for example:

...
printf("Diga qual o nome da banda: ");
gets((*banda)[i].nome);
...

Below is a functional version of the program with these changes:

#include <stdio.h>
#include <stdlib.h>

#define TAM 2

typedef struct
{
    char nome[20];
    char tipo[15];
    int integrantes,posicao;
} BANDAS[TAM];

void ler (BANDAS *banda);
void mostrar (BANDAS banda);

int main()
{
    BANDAS banda;

    ler (&banda);
    mostrar(banda);
    getchar();
    return 0;
}

void ler (BANDAS *banda)
{
    int i;
    for (i=0; i<TAM; i++)
    {
        printf("Diga qual o nome da banda: ");
        gets((*banda)[i].nome);
        printf("Tipo de musica: ");
        gets ((*banda)[i].tipo);
        printf("Quantos integrantes tem a banda: ");
        scanf("%d",&(*banda)[i].integrantes);    
        printf("Posicao no seu top 5: ");
        scanf("%d",&(*banda)[i].posicao);    
        getchar();
    }    
}

void mostrar (BANDAS banda)
{
    int i;
    for (i=0; i<TAM; i++)
    {
        printf ("Nome: %s\n",banda[i].nome);
        printf ("Tipo de musica: %s\n",banda[i].tipo);
        printf ("Numero de integrantes: %d \n",banda[i].integrantes);
        printf ("Posicao no seu TOP 5: %d \n",banda[i].posicao);
    }
}

See working on IDEONE

---

Although the program works this way, you can make it more readable by changing the declaration of the struct to store only the data of a band, and create the array within the function main().

Two other tips:

1. Only use the typedef where it is really necessary, which is not the case for such programs (simple).
2. The command __fpurge is not part of the standard language C and should be avoided.