iPhone UIViews - how to associate variables with UIView?

I am new to iphone and xcode. This may be a very simple question but I could not find an example code in books. I want to do the following:

• Have 2 UIView on the screen
• Each view will step through the color of the rainbow (r开发者_StackOverflow中文版ed/orange/yellow/green/blue/indigo/violet) using gesture recognizer, e.g., if the current color is green, if the user swipes up the UIView changes to yellow, if the user swipes down the UIView changes to blue.
• Hence, each view will need to keep the current color and respond to the swipes accordingly.

I understand how to implement the detection of swipes using gesture recognizer but I don't know how to have each view keep a separate variable for the current color. I want a generic code because there will be more than 2 UIViews in my application once I figure out how it is done.

Thanks in advance.

You can subclass UIView to include any variables that you like:

ColorSwiperView.h

@interface ColorSwiperView : UIView
{
    ColorType currentColor;
}
@property (nonatomic, assign) ColorType currentColor;
@end

ColorSwiperView.m

@implementation ColorSwiperView
@synthesize currentColor;

- (id)initWithFrame:(CGRect)frameRect
{
    if ((self = [super initWithFrame:frameRect]) == nil) { return nil; }
    currentColor = red;
    return self;
}

@end

To be used as follows:

#import "ColorSwiperView"

...

ColorSwiperView * cView = [[ColorSwiperView alloc] initWithFrame:...];
cView.currentColor = green;

Note: this assumes that you have defined an enum for the colors:

typedef enum
{
    red = 0,
    green = 1,
    ...
}
ColorType;

perhaps defining a subclass of UIView something like:

@interface RainbowView : UIView {
    UIColor *currentColor;
}

@property (nonatomic, retain) UIColor *currentColor;
@end

and creating 2 (or more) views of that class in your view controller as outlets (if you're using interface builder):

@class RainbowView;
@interface RainBowViewController : UIViewController {
     RainbowView *rainbowView1;
     RainbowView *rainbowView2;
}

@property (nonatomic, retain) IBOutlet RainbowView *rainbowView1;
@property (nonatomic, retain) IBOutlet RainbowView *rainbowView2;
@end

Since you are going to maintain an array of colors, say colorsArray, and assign views their color from that selection. You can do this in the swipe handler.

- (void)handleSwipe:(UISwipeGestureRecognizer*)swipeGesture {
    UIView *view = swipeGesture.view;

    NSInteger currentColorIndex = [colorsArray indexOfObject:view.backgroundColor];
    NSInteger nextColorIndex = currentColorIndex + 1;
    if ( nextColorIndex == [colorsArray count] ) {
        nextColorIndex = 0;
    }

    view.backgroundColor = [colorsArray objectAtIndex:nextColorIndex];
}

This way you don't need to subclass.

Subclassing

You can subclass UIView and add your own instance variables to it. Say,

@interface RainbowView: UIView {
    NSInteger currentColorIndex;
}

@property (nonatomic, assign) NSInteger currentColorIndex;
...

@end

@implementation RainbowView

@synthesize currentColorIndex;

...

@end

In your gesture handling method,

- (void)handleSwipe:(UISwipeGestureRecognizer*)swipeGesture {
    RainbowView *aView = (RainbowView*)swipeGesture.view;

    // Get the next color index to aView.currentColorIndex;
    aView.backgroundColor = [colorsArray objectAtIndex:nextColorIndex];
    aView.currentColorIndex = nextColorIndex;
}