iPhone UIViews - how to associate variables with UIView? - iphone

Question

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 (red/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.

Answer 1

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;

Answer 2

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

Answer 3

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;
}