Question

出于某种原因，我的变量文件名在从最近的类实例到setupView到filename时发生了变化，我无法弄清楚原因。我刚开始学习obj-C，所以我假设我正在做某种新手的错误。

它们通过以下方式实例化：

campusMapTileZero=[[CampusMapTile alloc] initNameOfTiletoLoad:@"cm0"];
campusMapTileOne=[[CampusMapTile alloc] initNameOfTiletoLoad:@"cm1"];

和我所指的实现是：

#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

问题是你的filename变量是全局变量，而不是实例变量。

您需要删除现有的NSString* filename声明，并在您的课程filename块中声明@interface，如下所示：

@interface CampusMapTile : UIViewController {
    NSString* filename;
}

Answer 2

在setTile中你只是指定指针，所以如果指针指向的字符串发生变化，你存储在类实例中的filename也会改变。尝试类似的事情：

-(void)setTile:(NSString*) _filename {
    NSLog(@"set tile called from setTile.");
    filename = [_filename copy];
    NSLog(@"filename in setTile is:");
    NSLog(filename);
}

这里的变量文件名如何变化？

2 个答案: