I have several objects in an array. These objects are from a UIImageView subclass.
These objects' class has several #synthesized properties.
At some point I have to create a duplicate of an object in a given position on the array at a different coordinate. Then I do:
id objectToDuplicate = [myArray objectAtIndex:x];
id newObject = [objectToDuplicate copy];
CGPoint newCenter = [objectToDuplicate center];
newCenter.x = newCenter.x + 10;
newCenter.y = newCenter.y + 10;
[newObject setCenter:newCenter];
[self.view addSubview:newObject];
[newObject release];
When this code runs, nothing happens. I mean, no object is created with a 10 pixel offset and I see this message in the console:
** ... copyWithZone:]: unrecognized selector sent to instance ... **
The objects have several elements such as text boxes, labels, and images that have shadow, glow, etc., and the new object has to have the same values for text colors, shadows, glows, size, images, etc., as the original.
I thought UIImageView had the NSCopying protocol in place. If this is the problem, how do I implement that?
Please refrain from sending me to the docs, I have read them and this is why I am asking here. Please give me practical examples.
Thanks.
Where did you read that UIImageView implements NSCopying? It doesn't, you have to do that yourself for your subclass.
Related
I am trying to find if collision occurs between two rectangles in objective-c. I thought one way to accomplish this would be detect the rectangle that is closest to 0,0 point then do rest of the work.
I wrote a function that takes two rectangle objects as parameters and does the math to calculate area, distance to origin etc....
So lets say rect1 is at (100,200) and rect1's width is 100 height 200, rect2 is at 150,150 and rect2's width is 100 height 200 this is calculated by function well enough.
If I switch rec1 and rect2 properties, so rect1 will be at 150,150 while rect2 will be at 100,200. And call following function
-(Rectangle*)intersect:(Rectangle*)rectA:(Rectangle*)rectB{
//check closest rectangle to 0,0 and switch rectangles
if (rectA.origin.x>rectB.origin.x) {
Rectangle *temporary = [[Rectangle alloc] init];
temporary=rectA;
rectA=rectB;
rectB=temporary;
[temporary release];
}
float rectAX = rectA.origin.x;
float rectAY = rectA.origin.y;
float rectBX = rectB.origin.x;
float rectBY = rectB.origin.y;
When I enable guard malloc and zombies I get following error:
-[Rectangle origin]: message sent to deallocated instance 0x100acffd0
As soon as rectA.origin.x; is called I get the error.
So Howcome rectA or rectB is deallocated? What is the correct way to switch two objects that has bunch of properties ?
There is a built in function for comparing CGRects CGRectIntersectsRect(rectA, rectB) that you can use to check your rectangle's frames :)
As far as your code for switching you have created a third object by allocing temporary. Then you set the temporary pointer at rectA and then you release rectA at the end since its pointing to temporary. Leaving the newly created object as a leak and then sending messages to the released rectA.
You don't really want to swap object pointers like that if you can help it in my experience. But if you absolutely have to and understand what's going on you could do it like this:
// Create copies of your objects
Rectangle *rectACopy = [rectA copy];
Rectangle *rectBCopy = [rectB copy];
// release the originals.
[rectA release];
[rectB release];
// Set your copies to the original pointers.
rectA = rectBCopy;
rectB = rectACopy;
NSCopying Protocol
First you need to implement the protocol.
#interface Rectangle : NSObject <NSCopying>
Then you need to create the new method. This will create a new object but with all the same values.
- (id)copyWithZone:(NSZone *)zone
{
id copy = [[[self class] alloc] init];
if (copy) {
// Copy NSObject based properties like UIViews, NSArrays, Subclassed objects.
[copy setObjectProperty:[self.objectProperty copy]];
// Set primitives like ints, CGRects, Bools.
[copy setPrimitiveProperty:self.primitiveProperty];
}
return copy;
}
You don't need to allocate a new object instance for temporary (and therefore you don't need to release it either). You are just taking your 2 existing pointers and switching them around. You're correct to use a 3rd variable (temporary) but you don't need to allocate any new space because you're not moving anything in memory, just swapping which variables point to the existing objects.
-(Rectangle*)intersect:(Rectangle*)rectA:(Rectangle*)rectB{
//check closest rectangle to 0,0 and switch rectangles
if (rectA.origin.x>rectB.origin.x) {
//Rectangle *temporary = [[Rectangle alloc] init]; // here you don't need to allocate as you are not using this object
// So use
Rectangle *temporary=rectA;
rectA=rectB;
rectB=temporary;
//[temporary release]; //you don't need this. Here you were releasing rectA not the temp rect that you allocated just below if, as you assign rectA to temporary
}
float rectAX = rectA.origin.x;
float rectAY = rectA.origin.y;
float rectBX = rectB.origin.x;
float rectBY = rectB.origin.y;
I'm trying to understand Automatic Reference Counting, as I come from a high-level programming language (Python) and I'm working on a project which use this feature of Objective-C. I often get problems with ARC deallocating objects which I need later, but now I got a concrete example for which I hope I'll get an explanation.
- (void) animateGun:(UIImageView *)gun withFilmStrip:(UIImage *)filmstrip{
NSMutableArray *frames = [[NSMutableArray alloc] init];
NSInteger framesno = filmstrip.size.width / gun_width;
for (int x=0; x<framesno; x++){
CGImageRef cFrame = CGImageCreateWithImageInRect(filmstrip.CGImage, CGRectMake(x * gun_width, 0, gun_width, gun_height));
[frames addObject:[UIImage imageWithCGImage:cFrame]];
CGImageRelease(cFrame);
}
gun.image = [frames objectAtIndex:0];
gun.animationImages = frames;
gun.animationDuration = .8;
gun.animationRepeatCount = 1;
[gun startAnimating];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW,(arc4random() % 300)/100 * NSEC_PER_SEC), dispatch_get_current_queue(),^{
[self animateGun:leftGun withFilmStrip:[self getFilmStripForAction:gunShoot andTeam:nil withWeapon:nil]];
});
}
The idea behind this snippet of code is simple: I have a (UIImageView*)gun which I animate with the images stored in (NSMutableArray *)frames, at random times. (UIImage *)filmstrip is just an image which contains all the frames which will be used on animation. The first iteration of animation works, but the problems appears on the second iteration, where I get -[UIImage _isResizable]: message sent to deallocated instance ... or -[UIImage _contentStretchInPixels]: message sent to deallocated instance ... or -[NSArrayI release]: message sent to deallocated instance .... This happens at
gun.animationImages = frames;
but I don't understand why. I'm not requesting a fix for my issue, but just to help me understand what's happening here. Thanks.
ARC is a mechanism that removes the need to manually retain/release objects. Here's a nice site that explains how this works: http://longweekendmobile.com/2011/09/07/objc-automatic-reference-counting-in-xcode-explained/
Try changing "leftGun" for "gun". I think that's probably the one that gets deallocated at some point, if you're using it through an ivar. Otherwise, leftGun simply isn't in the scope.
Here's what it should look like:
In your .h file:
#property (nonatomic, strong) IBOutlet UIImageView *leftGun;
In your .m file:
dispatch_after(dispatch_time(DISPATCH_TIME_NOW,(arc4random() % 300)/100 * NSEC_PER_SEC), dispatch_get_current_queue(),^{
[self animateGun:gun withFilmStrip:[self getFilmStripForAction:gunShoot andTeam:nil withWeapon:nil]];
});
Also, not quite sure where "gunShoot" is coming from. Is that supposed to be an enum?
EDIT
Added an example of how the leftGun property should be defined. The reason behind using a property over an ivar is for memory management purposes. If you want to release or destroy an object that is a property, simply set it to nil and the property will take care of releasing the object if it has to.
You may prevent the deallocation of the frames array if you mark it as __block.
__block NSMutableArray *frames = [NSMutableArray array];
see “The __block Storage Type.”
I am making a simple game that requires that I draw multiple UIImages in many different places. My problem here is that I need to add the UIImages to an NSMutableArray, and access them later. Using NSStrings to represent the images (such as for paths) will not work here, so I need to know how to change the images for every UIImage in the array.
My code is as follows (at least, for accessing the NSMutableArray). The NSMutableArray is declared in my .h file, and is initialized in a different method.
for (int a = 0; a <= [theArray count]; a ++) {
// I make a UIImage, which I will draw later
UIImage *theImage = [theArray objectAtIndex:a];
// then I do the drawing
}
This works fine. My problem is that I cannot figure out how to change a particular object in the NSMutableArray. How can I do this?
By the way, I am adding the UIImages to the NSMutableArray with the following code.
+ (void) createCarWithImage:(NSString*)theImageName {
UIImage *anImage= [UIImage imageNamed:theImageName];
[theArray addObject:anImage];
}
I think you want to use this method:
- (void)replaceObjectAtIndex:(NSUInteger)index withObject:(id)anObject
e.g.:
[theArray replaceObjectAtIndex:4 withObject:someOtherImage];
Just modify each UIImage in the NSMutableArray as is, you only have a pointer to the actual data. That is, regardless of what pointer you use to change the data, the data is changed for every pointer.
Additionally, you can also iterate over your UIImages with:
for (UIImage *img in theArray)
{
//send messages to img
}
Answer to Comment
You can modify the UIImage at index 4 by:
UIImage *image = [theArray objectAtIndex:4];
//send messages to image
I am working on a game in OBJ C that has a ball view and a stage view. The stage view has 4 subviews. All views are UIImageViews. I have a method for collision detection that is working. I would like to expand it to more than 4 subviews without simply creating more lines of code. Looking at the code below, is there a way to simplify this into loops instead. Thanks!
// convert each square to be relevant to ball's superview in order to collision detect
CGRect square_01Frame = [ball.superview convertRect:square_01.frame fromView:square_01.superview];
CGRect square_02Frame = [ball.superview convertRect:square_02.frame fromView:square_02.superview];
CGRect square_03Frame = [ball.superview convertRect:square_03.frame fromView:square_03.superview];
CGRect square_04Frame = [ball.superview convertRect:square_04.frame fromView:square_04.superview];
// convert CGRects to NSStrings for storage in square_frames array
NSString *square_01FrameString = NSStringFromCGRect(square_01Frame);
NSString *square_02FrameString = NSStringFromCGRect(square_02Frame);
NSString *square_03FrameString = NSStringFromCGRect(square_03Frame);
NSString *square_04FrameString = NSStringFromCGRect(square_04Frame);
// load array of NSStrings
[square_frames replaceObjectAtIndex:0 withObject:square_01FrameString];
[square_frames replaceObjectAtIndex:1 withObject:square_02FrameString];
[square_frames replaceObjectAtIndex:2 withObject:square_03FrameString];
[square_frames replaceObjectAtIndex:3 withObject:square_04FrameString];
// create a for loop
for (int i=0; i<4; i++) { // 4 squares
// create test frame
CGRect test_frame = CGRectFromString([square_frames objectAtIndex:i]);
if (CGRectIntersectsRect(test_frame,ball.frame)) { // collision detection
// do something
}
}
Well, I would do a number of things.
First, I would create a ball "model", just an NSObject subclass to represent the Ball. Probably, that would have a property "location" or something, which is the CGRect.
Then, your current view could have an array of ball objects on the screen, and just loop through them.
Overall, though, I don't think using UIView's rects is the best way to manage collision detection. I think you'd be better off defining that in some other way, and then simply updating the UI accordingly.
Generally, it's not a good idea to rely on your UI implementation for game design. It makes it hard to change (as you note in your question).
I have an NSArray of custom NSObjects. Each object has some properties and an image that I would like to display in a grid view. NSMatrix appears to be a good solution to my problem, but I am having issues getting the content of the objects to display.
Couple of things to note.
I am not using core data
I am trying to do this programmatically
I have considered using NSCollectionView but NSMatrix appears to be a better solution in this case
All the cells follow the same display format as each other - i.e. I'm not wanting to pass different cells different types of objects, just a different instance of the object
Assume I have an NSView (matrixContainerView) in a window. The controller file has an IBOutlet to matrixContainerView. In my controller I have the following in my awakeFromNib:
NSMatrix* matrix = [[NSMatrix alloc]
initWithFrame:[matrixContainerView bounds]
mode:NSRadioModeMatrix
cellClass:[MyCustomCell class]
numberOfRows:5
numberOfColumns:5];
[matrix setCellSize:NSMakeSize(116, 96)];
[matrix setNeedsDisplay:YES];
[matrixContainerView addSubview:[matrix autorelease]];
[matrixContainerView setNeedsDisplay:YES];
The class MyCustomCell header looks like the following:
#interface MyCustomCell : NSCell {
MyModel * theObject;
}
-(MyModel *)theObject;
-(void)setTheObject:(MyModel *)newValue;
And the implementation file as follows (drawing simplified):
#implementation MyCustomCell
-(void)drawInteriorWithFrame:(NSRect)theFrame inView:(NSView *)theView {
...drawing code using MyModel e.g. [MyModel isValid] etc...
}
-(MyModel *)theObject {
return theObject;
}
-(void)setTheObject:(MyModel *)newValue {
[theObject autorelease];
theObject = [newValue retain];
}
#end
After some initialization and population of the array containing MyModel objects in the controller, I want to populate the NSMatrix with instances of the objects.
How do I do this?
I have tried adding just two objects from the array as follows (just as a test):
MyCustomCell * cellOne = (MyCustomCell *)[matrix cellAtRow:0 column:0];
[cell setTheObject:[myArrayOfObjects objectAtIndex:0]];
MyCustomCell * cellTwo = (MyCustomCell *)[matrix cellAtRow:0 column:1];
[cellTwo setTheObject:[myArrayOfObjects objectAtIndex:1]];
But this just creates the first object image. If the above had worked, it would been a straightforward task of enumerating through the array and adding the objects.
How do I go about adding the cells and passing the appropriate objects to those cells in order that they can be displayed correctly?
The Apple docs are sparse to say the least on NSMatrix as far as the programming guide goes. The information in there is very useful to me, but only after I have added the objects and got them displaying!
Update
If I do not add the two objects (as per my example above) the output is no different, i.e. a single representation of my custom cell is drawn to screen. This tells me that the single representation I see is being done at the initialization of the matrix and in fact I wasn't drawing anything to column 0 row 0 when in fact I thought I was. Which leaves me now more confused.
Might be that the matrix actually has the two cells but its frame is too small to display them?
After adding the cells try calling [matrix sizeToCells]