问题
It was suggested that I use this line of code to call an image from my resources folder/project bundle. I also see it being used exactly like this on many different website tutorials.
NSBundle *mb=[NSBundle mainBundle];
NSString *fp=[mb pathForResource:@"topimage" ofType:@"PNG"];
NSImage *image=[NSImage initWithContentsOfFile:fp];
HOWEVER, I am receiving the following warning:
NSImage may not respond to +initWithContentsOfFile+
The documentation for NSImage shows that initWithContentsOfFile is in fact a method that should work. What might I be missing here?
回答1:
You're missing an +alloc
NSImage* image = [[NSImage alloc] initWithContentsOfFile:fp];
You can also use +imageNamed:, which fetches images from your main bundle.
NSImage* image = [NSImage imageNamed:@"topImage.png"];
回答2:
initWithContentsOfFile: is an instance method, but you're sending that message to the NSImage class. You need to send it to an instance—specifically, a freshly-allocated instance.
That's where alloc comes in. It's a class method that allocates an instance, which you then immediately send the init… message (as Darren showed).
Don't forget to release the instance when you're done with it. I generally autorelease the instance immediately after initing it; then, Cocoa will release the instance for me at an appropriate time. See the Memory Management Programming Guide for Cocoa for more information.
来源：https://stackoverflow.com/questions/1659407/cocoa-problem-with-this-code-using-nsbundle