Check whether +[UIImage imageNamed:] found an image - objective-c

Question

I have an long if statement to decide what image to show in a UIImageView. They are all .png files, and I use the code:
if (whatever) {
image = [UIImage imageNamed: #"imageName.png"];
}
Does anyone know of a way to check to see if the program can find the image? So that if the image does not exist in the program, it can display an error image or something?

Answer 1

+[UIImage imageNamed:]
will return nil if it couldn't find a corresponding image file. So just check for that:
UIImage *image = [UIImage imageNamed:#"foo.png"];
if (image == nil)
{
[self displayErrorMessage];
}

Answer 2

The shortest snippet would be
image = [UIImage imageNamed:#"imageName"] ? : [UIImage imageNamed:#"fallback_image"]
but do you really want such code?
Make another check:
if (whatever) {
image = [UIImage imageNamed: #"imageName.png"];
if(image == nil) {
image = [UIImage imageNamed: #"fallback_image"];
}
}
it still can be shorted, like
if(! (image = [UIImage imageNamed: #"imageName.png"]) ) {
...
}
but you're toying with readability here.

Answer 3

First, I'd suggest using a dictionary instead of a long if. You can key each image name by whatever. If whatever isn't currently an object, make an enum that will encapsulate that information and use NSNumbers to box the values of the enum.
Then, you can check for nil when you try to retrieve the image. imageNamed: uses nil to indicate failure, so:
if( !image ){
// No image found
}