如何在 char* 中输入值？

Question

typedef struct inventory
{
     char *name;
     int quantity;
} invent;

int main()
{
   invent *one=malloc(sizeof(invent));
   scanf("%s", one->name);
   ...
}

scanf() 不起作用。 还有其他方法吗？ 我想如何在 char* 中输入值。

Answer 1

您需要为name 成员进行第二次分配：

#define MAX_INPUT_LENGTH 20 // or however long your input needs to be
...
/**
 * Allocate space for the struct instance.
 */  
invent *one = malloc( sizeof *one );
if ( !one )
{
  fprintf( stderr, "memory allocation for one failed, exiting...\n" );
  exit( EXIT_FAILURE );
}

/**
 * At this point, one->name is uninitialized and doesn't point anywhere
 * meaningful.  Perform a second allocation to set aside space for the
 * input string itself.  Remember to account for the string terminator.
 */
one->name = malloc( sizeof *one->name * (MAX_INPUT_LENGTH + 1) ); 
if ( !one->name )
{
  fprintf( stderr, "memory allocation for one->name failed, exiting...\n" );
  exit( EXIT_FAILURE );
}

/**
 * At this point, we can store a string in one->name
 */
scanf( "%s", one->name );

完成后，按照分配的相反顺序解除分配：

free( one->name );
free( one );