I am receiving the following error: expected identifier or '(' - c

Question

The error is referencing the following line of code:
tenant[i].name = get_string("Enter the residents name: ");
and has an arrow pointing at the period . between tenant[i] and name. I am not sure what I am missing.
typedef struct {
string name;
int apt;
} tenant;
int n;
int numres(void);
string nameres(int numres);
int apt(int numofres);
int main(void) {
int numres(void);
tenant tenants[n];
string nameres(int n);
int apt(int n);
for (int m = 0; m < n; m++) {
printf("Resident %s resides in apt# %i\n",
tenants[m].name, tenants[m].apt);
}
return 0;
}
//this function prompts the user for the number of residents
int numres(void) {
do {
n = get_int("Enter the number of residents: ");
} while (isalpha(n) != 0 || isspace(n) != 0);
return n;
}
// this function prompts the user for the residents names.
string nameres(int numres) {
int i = 0;
do {
tenant[i].name = get_string("Enter the residents name: ");
return tenant[i].name;
i++;
} while (i < numres);
}
// this function prompts the user for the residents apt number
int apt(int numofres) {
for (int i = 0; i < numofres; i++) {
tenant[i].apt = get_int("Enter residents apt number: ");
return tenant[i].apt;
}
}

Answer 1

There are multiple problems in the code:
the string type is not a standard C type, it is defined in <cs50.h> as a typedef for char *, which can be quite confusing. Make sure you include <cs50.h> and <stdio.h>.
in the main function, you define tenant tenants[n];, an array with a length specified by a variable that has a value of 0: this has undefined behavior, and the array cannot be used for anything.
in the main function, you declare functions int numres(void);, string nameres(int n); and int apt(int n);. Such declarations should be made at the file scope, and indeed are done so already. You probably meant to call the functions instead, so you should write:
int main(void) {
numres();
tenant tenants[n];
nameres(n);
apt(n);
for (int m = 0; m < n; m++) {
printf("Resident %s resides in apt# %i\n",
tenants[m].name, tenants[m].apt);
}
return 0;
}
But passing the value of n as a global variable is cumbersome and confusing. numres() should return the value and n should be a local variable.
in numres, it does not make sense to test isalpha(n) != 0 || isspace(n) != 0 because n is a number, not the value of a byte read from the input stream. The function get_int already checks for valid input and returns a converted number, you should just check that the number is positive: n > 0.
nameres should be defined as a void function and use a for loop for the case where n has the value 0.
in nameres and apt should receive tenants as an argument as this array is defined locally in main. The code should use tenants instead of tenant, which is a type name. This is the reason for your compilation issue. Using a _t suffix for the types is recommended to avoid such problems.
in nameres and apt should should prompt for the name and apartment numbers of all residents, remove the return statements.
using while or for loops instead of do / while loops allows for more concise code with explicit tests closer to the generating fact.
Here is a modified version:
#include <cs50.h>
#include <stdio.h>
typedef struct tenant_t {
string name;
int apt;
} tenant_t;
int numres(void);
void nameres(tenant_t tenants[], int numres);
void apt(tenant_t tenants[], int numres);
int main() {
int n = numres();
tenant_t tenants[n];
nameres(tenants, n);
apt(tenants, n);
for (int i = 0; i < n; i++) {
printf("Resident %s resides in apt# %i\n",
tenants[i].name, tenants[i].apt);
}
return 0;
}
// this function prompts the user for the number of residents
// it returns the number which must be strictly positive
int numres(void) {
for (;;) {
int n = get_int("Enter the number of residents: ");
if (n > 0)
return n;
}
}
// this function prompts the user for the residents names.
void nameres(tenant_t tenants[], int numres) {
for (int i = 0; i < numres; i++) {
tenants[i].name = get_string("Enter the residents name: ");
}
}
// this function prompts the user for the residents apt number
void apt(tenant_t tenants[], int numres) {
for (int i = 0; i < numres; i++) {
tenants[i].apt = get_int("Enter residents apt number: ");
}
}