how is the variable filename here changing? - objective-c

Question

For some reason, my variable filename changes by the time it gets to setupView to filename from a more recent instance of the class and i cant figure out why. I just started learning obj-C, so im assuming im doing some sort of rookie mistake.
They are instantiated by:
campusMapTileZero=[[CampusMapTile alloc] initNameOfTiletoLoad:#"cm0"];
campusMapTileOne=[[CampusMapTile alloc] initNameOfTiletoLoad:#"cm1"];
and the implementation im referring to is:
#import "CampusMapTile.h"
#import "TileManager.h"
#import "GLView.h"
#import "OpenGLCommon.h"
#import "ConstantsAndMacros.h"
#implementation CampusMapTile
NSString *filename;
- (id) initNameOfTiletoLoad: (NSString *)filename
{
if(self = [super init]) {
NSLog(#"initialized map tile for tile:");
NSLog(filename);
[self setTile:filename];
}
return self;
}
-(void)setTile:(NSString*) _filename {
NSLog(#"set tile called from setTile.");
filename=_filename;
NSLog(#"filename in setTile is:");
NSLog(filename);
}
- (void)drawView:(GLView*)view
{
glBindTexture(GL_TEXTURE_2D, texture[0]);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
static const Vertex3D vertices[] = {
{0,0, 1}, //TL
{ 1024,0, 1}, //TR
{0,-1024, 1}, //BL
{ 1024.0f, -1024.0f, 1} //BR
};
static const GLfloat texCoords[] = {
0.0, 1.0,
1.0, 1.0,
0.0, 0.0,
1.0, 0.0
};
glVertexPointer(3, GL_FLOAT, 0, vertices);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}
- (void)setupView:(GLView*)view {
NSLog(#"setup view called");
NSLog(filename);
[self loadTextures:filename textureIdentifier:0];
}
-(void)loadTextures:(NSString*) filename textureIdentifier:(int) textureNumber {
//enable textures.
glEnable(GL_TEXTURE_2D);
glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_FASTEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// Bind the number of textures we need.
glGenTextures(1, &texture[textureNumber]);
glBindTexture(GL_TEXTURE_2D, texture[textureNumber]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
// [tileManager setupView:view];
NSString *path = [[NSBundle mainBundle] pathForResource:filename ofType:#"jpg"];
NSData *texData = [[NSData alloc] initWithContentsOfFile:path];
UIImage *image = [[UIImage alloc] initWithData:texData];
if (image == nil)
NSLog(#"Do real error checking here");
GLuint width = CGImageGetWidth(image.CGImage);
GLuint height = CGImageGetHeight(image.CGImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( height * width * 4 );
CGContextRef context = CGBitmapContextCreate( imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
// Flip the Y-axis
CGContextTranslateCTM (context, 0, height);
CGContextScaleCTM (context, 1.0, -1.0);
CGColorSpaceRelease( colorSpace );
CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);
CGContextRelease(context);
free(imageData);
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
#pragma mark - View lifecycle
/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView
{
}
*/
/*
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{
[super viewDidLoad];
}
*/
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#end

Answer 1

The problem is that your filename variable is a global variable, not an instance variable.
You need to delete your existing NSString* filename declaration and instead declare filename in your class's #interface block, like so:
#interface CampusMapTile : UIViewController {
NSString* filename;
}

Answer 2

in setTile you're just assigning pointers so if the string that the pointer is point to changes, the filename you store in the class instance will also change. try something like:
-(void)setTile:(NSString*) _filename {
NSLog(#"set tile called from setTile.");
filename = [_filename copy];
NSLog(#"filename in setTile is:");
NSLog(filename);
}