问题
If I assign an image to a UIImage view in a xib, is that image cached so that if I access the image using UIImage imageNamed: I am getting cached Image data?
I'm using iOS 5.1
回答1:
UIImage imageNamed: does its own cacheing of any images you use. The first time you use it for a given image, it'll populate the cache, and subsequently it'll use the cached version.
UIImageView in Interface Builder takes a string to tell it what image to use. It appears that the object that is actually encoded in the Xib to represent the image is a private class called UIImageNibPlaceholder, which contains a private NSString variable called runtimeResourceName. It's this class that implements the initWithCoder: method which is used when the system is loading objects from a xib.
So, the question is, inside UIImageNibPlaceholder's initWithCoder:, does it use the imageNamed: function of UIImage? I think it's reasonable to assume that it does, since the thing stored in the xib is the string runtimeResourceName, and the system is turning that string into an actual image when loading the xib.
This post on the Apple developer forums seems to clarify the point (under NDA so I can't copy it here). I couldn't find any publicly accessible information on the subject.
来源：https://stackoverflow.com/questions/10398547/are-images-assigned-in-a-xib-cached