Question

I am new to programming with Objective-C and Stackoverflow, and I need some help.

I’m trying to get an object from a NSMutableArray and check one of its internal properties. I figured the best way to do this is by doing the following cast:

GenericRoom *room = (GenericRoom*)[myRooms objectAtIndex: currentIndex + side];

if (room.myType == EMPTY) {
    return YES;
}

The problem is that when I create a class of type GenericRoom, your constructor already defines myType as EMPTY. When I insert the instances in NSMutrableArray, I changed to myType TAVERN this way:

NSMutableArray *myRooms = [[NSMutableArray alloc] initWithCapacity:15];

for (int i = 0: i <15: i + +) {
    GenericRoom tmpRoom * = [[GenericRoom alloc] initWithType: TAVERN];
    myRooms insertObject: tmpRoom atIndex i];
}

But when I do the cast that quote up there, it simply creates a new instance of the object GenericRoom, instead of copying the object inside NSMutableArray, making its result is always YES, my failing vereficação.

Is there any better way to solve this problem?
Thank you all.

EDIT: The complete code

GenericRoom.h

#import <Foundation/Foundation.h>
#import "cocos2d.h"

enum Rooms {
    EMPTY, TAVERN, WARRIORGUILD, MAGEGUILD
}roomsType;

@interface GenericRoom : CCLayer {
    CCSprite *mySprite;
    enum Rooms myType;
}

@property (nonatomic, retain) CCSprite *mySprite;
@property enum Rooms myType;
@property int test;

- (id)initWithSprite: (NSString *)file;
- (id)initWithType: (enum Rooms)roomType;

@end

GenericRoom.m

#import "GenericRoom.h"
@implementation GenericRoom
@synthesize mySprite, myType, test;

-(id)init {
    if (self = [super init]) {

    }
    return self;
}

-(id)initWithType: (enum Rooms) roomType {
    if (self = [super init]) {
        myType = roomType;

    }
    return self;
}

-(id)initWithSprite: (NSString *)file {

    if (self = [super init]) {
        mySprite = [CCSprite spriteWithFile:file];

        [self addChild: mySprite];
    }

    return self;
}
@end

RoomManager.h

#import <Foundation/Foundation.h>
#import "cocos2d.h"
#import "GenericRoom.h"
#import "RoomTavern.h"
#import "RoomEmpty.h"

enum Sides {
    LEFT, RIGHT, UP, DOWN
}theSides;

@interface RoomManager : CCLayer {
    CGSize size;
    NSMutableArray *myRooms;
}

- (void) CreateRoom: (enum Rooms)roomType;


@end

RoomManager.m

@implementation RoomManager

-(id)init {

    if (self = [super init]) {
        size = [[CCDirector sharedDirector] winSize];
        myRooms = [[NSMutableArray alloc] initWithCapacity:15];

        for (int i = 0; i < 15; i++) {
            GenericRoom *tmpRoom = [[GenericRoom alloc] initWithType:TAVERN];
            tmpRoom.test = 10;
            [myRooms insertObject:tmpRoom atIndex:i];
        }

        [self CreateRoom:TAVERN];
    }

    return self;
}

- (void) CreateRoom: (enum Rooms)roomType {
    switch (roomType) {
        case TAVERN:
        {
            //Create the Tavern Main Room
            RoomTavern *tmpRoom = [[RoomTavern alloc] initWithSprite:@"room-hd.png"];
            tmpRoom.mySprite.position = ccp(size.width/2,size.height/2);

            [self addChild:tmpRoom];

            [myRooms removeObjectAtIndex:8];
            [myRooms insertObject:tmpRoom atIndex:8];

            if ([self CheckAdjacentRooms:8 andSide:LEFT]) {
                RoomEmpty *tmpEmptyRoom = [[RoomEmpty alloc] initWithSprite:@"roomToBuild-hd.png"];
                tmpEmptyRoom.mySprite.position = ccp(tmpRoom.mySprite.position.x - tmpRoom.mySprite.contentSize.width, tmpRoom.mySprite.position.y);

                [self addChild:tmpEmptyRoom];

                [myRooms insertObject:tmpEmptyRoom atIndex:7];
            }

            break;
        }

        default:
            break;
    }
}

- (BOOL) CheckAdjacentRooms: (int)currentIndex andSide:(enum Sides)side {
    int leftRightSide = 0;
    if(side == LEFT)
        leftRightSide = -1;
    else if (side == RIGHT) 
        leftRightSide = 1;

    GenericRoom *roomTmp  = (GenericRoom *)[myRooms objectAtIndex:currentIndex + side];

    if (roomTmp.myType == EMPTY) {
        return YES;
    }
    else
        return NO;
}

@end

Answer 1

To enhance @Dan F answer. Read this …

http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/objectivec/Chapters/ocObjectsClasses.html#//apple_ref/doc/uid/TP30001163-CH11-SW7

… what’s nil messaging. Your locally declared myRooms variable hides your myRooms property (= instance variable). In other words, myRooms is nil. And what happens …

GenericRoom *room = (GenericRoom*)[myRooms objectAtIndex: currentIndex + side];

Because of nil messaging rules, [myRooms objectAtIndex:...] returns nil, thus your room is set to nil.

if (room.myType == EMPTY) {
    return YES;
}

And room.myType sends message myType to room object. And because room is nil, return value is 0 – enums does contain integer scalar values – this is the reason why it returns 0. And I assume that EMPTY is first element in your enum = has value 0. And 0 == 0 => returns YES even when your myRooms instance variable is nil.