imageNamed: is a method of the UIImage class in iOS. It is a convenience method for loading images without specifying any path information and storing them in a cache.
Explanation from the Apple documentation:
imageNamed: Returns the image object associated with the specified filename.
+ (UIImage *)imageNamed:(NSString *)name
Parameters
name
The name of the file. If this is the first time the image is being loaded, the method looks for an image with the specified name in the application’s main bundle.
Return Value
The image object for the specified file, or nil if the method could not find the specified image.
Discussion
This method looks in the system caches for an image object with the specified name and returns that object if it exists. If a matching image object is not already in the cache, this method loads the image data from the specified file, caches it, and then returns the resulting object.
On a device running iOS 4 or later, the behavior is identical if the device’s screen has a scale of 1.0. If the screen has a scale of 2.0, this method first searches for an image file with the same filename with an @2x suffix appended to it. For example, if the file’s name is button, it first searches for button@2x. If it finds a 2x, it loads that image and sets the scale property of the returned UIImage object to 2.0. Otherwise, it loads the unmodified filename and sets the scale property to 1.0. See iOS App Programming Guide for more information on supporting images with different scale factors.
Special Considerations
On iOS 4 and later, if the file is in PNG format, it is not necessary to specify the .PNG filename extension. Prior to iOS 4, you must specify the filename extension.
Availability
Available in iOS 2.0 and later.
