I'm relatively new to C and trying to understand structs and pointers. What does the *Building at the end of this struct declaration do?
typedef struct building { char *floor; struct building *nextBuilding; } *Building; Does it mean that from now on when I do
Building someBuilding = malloc(sizeof(struct building)); somebuilding is a pointer to a building?
Yes, when you write:
typedef struct building { … } *Building; Building bp; then bp is a pointer to a struct building. However, it is frequently regarded as bad style to include the pointer in the typedef; code is easier to understand if you use:
typedef struct building { … } Building; Building *bp; Now it is clear looking at the definition of bp that the type is a pointer. If you are never going to access the internals of the structure, then it doesn't matter too much (but look at FILE * in <stdio.h>; you always write FILE *fp, etc). If you're going to access the internals:
printf("Floor: %s\n", bp->floor); then it is better to have the pointer visible. People will be mildly surprised to see Building bp; and then later bp->floor instead of bp.floor.
To answer the question: yes. You now have a type Building that is a pointer to a struct building and you can do this:
Building someBuilding = malloc(sizeof(struct building)); someBuilding->floor = malloc (sizeof(char)*20); strcpy(someBuilding->floor, "First floor"); someBuilding->nextBuilding = NULL; etc.
note that this might not be a good idea in all cases. For example if you declare a method:
void setFloorName(Building building, char* name) you can't really tell that you need to pass a pointer to a building struct, but if you do:
void setFloorName(Building* building, char* name) you immediately see that the function takes a pointer.
