初始化自定义类时出现问题（UIImageView 可能无法响应“-alloc”）
我对这一行有一个问题，
ball* balle = [[ball alloc] initWithPNGFileName:ballPath andGame:game andCGRect:CGRectMake( 200, 100, 16, 16 )] ;
问题是“球未声明”，并带有警告：“UIImageView”可能不会响应“-alloc”和警告：没有找到“-initWithPNGFileName：andGame：andCGRect：”方法
这是方法：
-(id) initWithPNGFileName:(NSString *) filename andGame: (Game*) game andCGRect: (CGRect) imagerect_ {
[super init];
CGDataProviderRef provider;
CFStringRef path;
CFURLRef url;
const char *filenameAsChar = [filename cStringUsingEncoding:[NSString defaultCStringEncoding]]; //CFStringCreateWithCString n'accepte pas de NSString
path = CFStringCreateWithCString (NULL, filenameAsChar, kCFStringEncodingUTF8);
url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, NO);
CFRelease(path);
provider = CGDataProviderCreateWithURL (url);
CFRelease (url);
image = CGImageCreateWithPNGDataProvider (provider, NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease (provider);
imageRect = imagerect_ ;
[game addToDraw: self] ;
[game addToTimer : self] ;
return self ;
}
-(void) draw: (CGContextRef) gc
{
CGContextDrawImage (gc, imageRect, image );
}
我不'不明白为什么 UIImageView 无法分配以及为什么我没有找到 '-initWithPNGFileName:andGame:andCGRect:' 方法
谢谢
I have an issue for this line
ball* balle = [[ball alloc] initWithPNGFileName:ballPath andGame:game andCGRect:CGRectMake( 200, 100, 16, 16 )] ;
the issue is ' ball undeclared' with warning: 'UIImageView' may not respond to '-alloc' and warning: no '-initWithPNGFileName:andGame:andCGRect:' method found
Here's the method:
-(id) initWithPNGFileName:(NSString *) filename andGame: (Game*) game andCGRect: (CGRect) imagerect_ {
[super init];
CGDataProviderRef provider;
CFStringRef path;
CFURLRef url;
const char *filenameAsChar = [filename cStringUsingEncoding:[NSString defaultCStringEncoding]]; //CFStringCreateWithCString n'accepte pas de NSString
path = CFStringCreateWithCString (NULL, filenameAsChar, kCFStringEncodingUTF8);
url = CFURLCreateWithFileSystemPath (NULL, path, kCFURLPOSIXPathStyle, NO);
CFRelease(path);
provider = CGDataProviderCreateWithURL (url);
CFRelease (url);
image = CGImageCreateWithPNGDataProvider (provider, NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease (provider);
imageRect = imagerect_ ;
[game addToDraw: self] ;
[game addToTimer : self] ;
return self ;
}
-(void) draw: (CGContextRef) gc
{
CGContextDrawImage (gc, imageRect, image );
}
I don't understand why UIImageView can't be allocated and why I have no '-initWithPNGFileName:andGame:andCGRect:' method found
Thanks
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从您提供的代码来看，您似乎有一个名为
ball的UIImageView实例。您确定您的类名为ball（顺便说一下，类名应以大写字母开头）并且它是.h- 文件已正确包含吗？一些背景信息：
alloc是一个类方法，您不会将其发送到实例 - 它的签名类似于+ (id) alloc;（注意这里的加号！）基本上，警告表示您尝试在对象上调用实例方法 alloc，该方法将具有签名- (id) alloc;（注意这里的减号！），如果它存在的话（很可能不是这种情况）。因此，编译器不会将ball识别为类名，而是将其识别为UIImageView的实例，正如警告所示，它可能不会响应- (id ）分配；.默认情况下，编译器假设未知方法返回
id的实例（而不是您期望的ball的实例），这就是为什么它警告您找不到该对象的名为-initWithPNGFileName:andGame:andCGRect的方法。From the code you provide it seems that you have an instance of
UIImageViewcalledball. Are you sure your Class is calledball(Class names should begin with a capital letter, by the way) and it's.h- file is properly included?Some background information:
allocis a class method, you don't send it to an instance - it's signature is something like+ (id) alloc;(mind the plus here!) Basically, the warning says that you try to invoke the instance method alloc on your object, which would have the signature- (id) alloc;(mind the minus here!), if it existed (which is most probably not the case). Therefore, the compiler recognizesballnot as a class name, but as an instance ofUIImageView, which - as the warning indicates - may not respond to- (id) alloc;.By default, the compiler assumes that unknown methods return an instance of
id(and not ofballas you expected), this is why it warns you that it can't find a method called-initWithPNGFileName:andGame:andCGRectfor this object.