Question

I’m using a header file to set the background for my application. I have something like:

#define backgroundImage [UIColor colorWithPatternImage:[UIImage imageNamed:@"background.jpeg"]] 

but I want use UIImageView instead of UIColor. I know I can do:

UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)
[imageView setImage:[UIImage imageNamed:@"background.png"]];
self.tableView.backgroundView = imageView;

but how do I use it with #define?

Answer 1

#define is a preprocessor directive. What this is going to do is anywhere you use backgroundImage you will get [UIColor colorWithPatternImage:[UIImage imageNamed:@"background.jpeg"]]

The best way to handle this is use the #define to specify the image name:

#define kBackgroundImage @"background.png"

And then use that in your code:

// Use the table view bounds so the background view is the size of the table view
UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.tableView.bounds;

[imageView setImage:[UIImage imageNamed:kBackgroundImage]];
self.tableView.backgroundView = imageView;

If you want to however, you can do:

#define kBackgroundImage [UIImage imageNamed:@"background.png"]

And:

// Use the table view bounds so the background view is the size of the table view
UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.tableView.bounds;

[imageView setImage:kBackgroundImage];
self.tableView.backgroundView = imageView;

If you choose to make the whole code block a preprocessor define, you can use \ to make new lines.

#define UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.tableView.bounds; \
[imageView setImage:[UIImage imageNamed:kBackgroundImage]]; \
self.tableView.backgroundView = imageView;