Some help with Pointers please

[Micko1]

Hello,

I am having some trouble with this function:

 
void room::addConnection(string direction, room *x)
{
    if (direction == "north")
    {
         north = x;
    }
}
 

How can I make the connection both ways? For example I connect room1 with room2 (north) as shown above, but how can I make it that it automatically joins room2 with room1 (south)

Thanks in advance!

[svlsr2000]

Hello,

I am having some trouble with this function:

 
void room::addConnection(string direction, room *x)
{
    if (direction == "north")
    {
         north = x;
    }
}
 

How can I make the connection both ways? For example I connect room1 with room2 (north) as shown above, but how can I make it that it automatically joins room2 with room1 (south)

Thanks in advance!

Can you post more code from your file. What do you mean by joining two rooms??

[Micko1]

Can you post more code from your file. What do you mean by joining two rooms??

I have a class called "room" I have 10 rooms (room1 room2.......room10) the rooms are connected via pointers (North, South, East,West). I have a function that creates all the rooms, and the code above is a section from the function that connects the rooms (room1 North leads to room2 and room2 South points to room1).

What I'm trying to achieve is a 2 way connection (North points to room2 and south points to room1)

Below is the entire function, ive commented what I'm trying to achieve. If you need more code let me know.

Thanks in advance :)

void room::addConnection(string direction, room *x) //x is next room
{
    if (direction == "north")
    {
         north = x; //points north pointer to next room (room passed)
         ?          //points next room south pointer to current room
 
 
    }
    else if (direction == "south")
    {
         south = x; //points south pointer to next room (room passed)
         ?          //points next room north pointer to current room
 
    }
    else if (direction == "east")
    {
         east = x;//points east pointer to next room (room passed)
         ?          //points next room west pointer to current room
 
    }
    else if (direction == "west")
    {
         west = x;//points west pointer to next room (room passed)
         ?          //points next room east pointer to current room
    }
}

[Ganon11]

I would add some code in each if...else branch that calls addConnection in x (which I presume is room2) - you'll have to use the opposite direction string and the this pointer.

Something you might run into is an infinite loop here - you set room1's connection, then call room2's connection, which in turn calls room1's connection, etc. etc. In order to fix this, I'd check to see if the current room's north/south/east/west pointer is NULL before setting the connection - if it's NULL, you're OK, but if it's not NULL, it's already been set and shouldn't be changed.

[weaknessforcats]

How can I make the connection both ways? For example I connect room1 with room2 (north) as shown above, but how can I make it that it automatically joins room2 with room1 (south)

It looks like you need to call:

void room::addConnection(string direction, room *x)
{
    if (direction == "north")
    {
         north = x;
         x->addConnection("south", this);
    }
}
 

Do I have that right?

[Ganon11]

It looks like you need to call:

void room::addConnection(string direction, room *x)
{
    if (direction == "north")
    {
         north = x;
         x->addConnection("south", this);
    }
}
 

Do I have that right?

Looks right, but keep in mind the infinite loop that will result. You need to prevent that somehow.

[Micko1]

ok cool, thankyou for the replies, I modified the fuction to check if the pointers are NULL, so it doesent keep looping :)

I have another question:

int main()
{    
    int movesLeft = 20;
 
    room * currentPlayerLocation;
    room currentRoom;
 
    currentPlayerLocation = currentRoom;
 
    //room * currentPlayerLocation = new room ("currentRoom;");
 
    createMaze(currentPlayerLocation);
 
    menu(movesLeft, currentPlayerLocation);
 
    system ("pause");
    return 0;
}
 

what is wrong with this?

I keep getting this error:

1>c:\documents and settings\comp\my documents\visual studio projects\room_latest\roomtest.cpp(17) : error C2440: '=' : cannot convert from 'room' to 'room *'


The commented section is another method I tried using, I get a fatal error.

Thankyou once again :)

[Ganon11]

int main()
{    
    int movesLeft = 20;
 
    room * currentPlayerLocation;
    room currentRoom;
 
    currentPlayerLocation = currentRoom;
 
    //room * currentPlayerLocation = new room ("currentRoom;");
 
    createMaze(currentPlayerLocation);
 
    menu(movesLeft, currentPlayerLocation);
 
    system ("pause");
    return 0;
}
 

currentPlayerLocation is a variable of type room* - it is a pointer to a room.

currentRoom is a variable of type room - it is a room.

You cannot assigm a room to a pointer. You could assign the address of a room to a pointer (currentPlayerLocation = &currentRoom), or the room pointed to by the pointer to a room (currentRoom = *currentPlayerLocation), but nothing else.

Also, I'm not sure what your room constructor expects, but I'm fairly certain it doesn't need a semicolon in there. Check what you're trying to do there and what your constructor accepts.

[Micko1]

Thanks for the reply, I appreciate it :)

Firstly, the semicolin was a typo :)

Even when I do as you say, I still get this error, I'm unsure what I'm getting wrong..

[Micko1]

all fixed :)

Thanks for all the help!

[karthickbabu]

hello

you use pointer variable inside the function like this.

north=*x;

U try like these


by
karthick

Hello,

I am having some trouble with this function:

 
void room::addConnection(string direction, room *x)
{
    if (direction == "north")
    {
         north = x;
    }
}
 

How can I make the connection both ways? For example I connect room1 with room2 (north) as shown above, but how can I make it that it automatically joins room2 with room1 (south)

Thanks in advance!