使用具有結構的指針將數據傳遞給函數

Question

這是一個類項目的程序。假設能夠創建和編輯結構。 CreatRec功能正常工作。對於ModifyRec，我試圖通過指針將數組發送給它，以避免「複製」數據。但是，我無法實際更改數組。 ATM底部的行（gr [change] .lastname = * info;）完全不起作用。我真的不知道我在這裏做錯了什麼。

#include "stdafx.h" 
#include <string.h> 
#include <stdlib.h> 

struct student{ 
    int recordname; 
    char lastname[10]; 
    char firstname[10]; 
    float math; 
    float english; 
    float science; 
}; 

//prototypes 
int menu(); 
struct student CreatRec(int); 
void ModifyRec(struct student*); 


void main() 
{ 
    int option, j;//option will be for users menu choice, j makes for loop work for creatrec 
    struct student grades[10]; 
    j = 0; 
    option=Menu(); 
    if (option == 1) 
     for (j = 0; j<10; j++) 
      (grades[j + 0]) = CreatRec(j); 
    else if (option==2) 
     ModifyRec(grades);//dont need & is smart bc array 


    printf("%s",grades[0].lastname);//This line is checking to see if ModifyRec actaully worked 

    //free(grades);2 
    while (1); 
} 


int Menu() 
{ 
    int choi; 
    printf("Please choose one of the following options.\n 1) Create New Student Records.\n 2) Modify an Existing Student Record\n"); 
    printf(" 3) Print a New Sutdent Record.\n 4) Quit\n"); 
    scanf("%d", &choi); 
    return choi; 
} 
struct student CreatRec(int i) 
{ 
    struct student qr; 
    //qr = (struct student*)malloc(sizeof(struct student)*6); 

    printf("RecordNum %i\n", i); 
    printf("Please enter last name-->"); 
    scanf("%s", &qr.lastname); 
    printf("Please enter first name-->"); 
    scanf("%s", &qr.firstname); 
    printf("Please math grade-->"); 
    scanf("%f", &qr.math); 
    printf("Please english grade-->"); 
    scanf("%f", &qr.english); 
    printf("Please science grade-->"); 
    scanf("%f", &qr.science); 
    return qr; 
} 

void ModifyRec(struct student gr[]) 
{ 
    int change; 
    char feild[10], info[10]; 

    printf("Which record would you like to change?\n"); 
    scanf("%d", &change); 
    rewind(stdin); 
    printf("Which feild would you like to edit?\n"); 
    scanf("%s", &feild); 
    rewind(stdin); 
    printf("Enter info\n"); 
    scanf("%s", &info); 

    if (!strcmp("lastname", feild)) 
     gr[change].lastname= *info;//NOT WORKING 

} 

Answer 1

gr[change].lastname是一個char數組，不是指針。你不能重新分配它。在這種情況下，您可能應該完成scanf("%s", gr[change].lastname);並跳過char info[10]。

Answer 2

首先我沒有看到一個偉大的意義在聲明中

for (j = 0; j<10; j++) 
     (grades[j + 0]) = CreatRec(j); 

的表達grades[j + 0]這些陳述

printf("Please enter last name-->"); 
scanf("%s", &qr.lastname); 
printf("Please enter first name-->"); 
scanf("%s", &qr.firstname); 

已被取代

printf("Please enter last name-->"); 
scanf("%s", qr.lastname); 
printf("Please enter first name-->"); 
scanf("%s", qr.firstname); 

而這個說法

if (!strcmp("lastname", feild)) 
    gr[change].lastname= *info;// 

必須被取代

if (!strcmp("lastname", feild)) 
    strcpy(gr[change].lastname, info);