How to undo multitouch drawing in iOS - ios

Question

Please help me to undo and forward my draw. I store all paths into an pathArray and now I want to undo and foward the path ( like app Notes (Apple) ).
Please help me to solve this!
This is my PathArray class
// PathArray.h
#import <Foundation/Foundation.h>
#interface PathArray : NSObject
#property (nonatomic) CGPoint start;
#property (nonatomic) CGPoint end;
#property (nonatomic) UIColor* color;
#property (nonatomic) CGFloat pathWidth;
- (instancetype) initWithStartPoint: (CGPoint)start andEnd: (CGPoint)end andColor: (UIColor *) color andPathWidth: (CGFloat) pathWidth;
#end
This is my Draw class
- (void)drawRect:(CGRect)rect
{
[strokecolor setStroke];
for (int i=0; i<pathArray.count; i++ ) {
CGContextRef contex = UIGraphicsGetCurrentContext();
CGContextSetLineCap(contex, kCGLineCapRound);
CGContextBeginPath(contex);
CGContextMoveToPoint(contex, pathArray[i].start.x, pathArray[i].start.y);
CGContextAddLineToPoint(contex, pathArray[i].end.x, pathArray[i].end.y);
CGContextSetStrokeColorWithColor(contex, pathArray[i].color.CGColor);
CGContextSetLineWidth(contex, pathArray[i].pathWidth);
CGContextStrokePath(contex);
}
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch* touch = [touches anyObject];
if ([touch type] == UITouchTypeStylus)
{
if(drawable){
[self.delegate changeScrollViewInteraction:NO];
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self];
}
}
else
{
[self.delegate changeScrollViewInteraction:YES];
return;
}
[super touchesBegan: touches withEvent: event];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
if ([touch type] == UITouchTypeStylus) //pencil touch
{
if(drawable){
CGPoint newpoint = [touch locationInView:self];
PathArray *paths = [[PathArray alloc]initWithStartPoint:lastPoint andEnd:newpoint andColor:strokecolor andPathWidth:pathWidth];
[pathArray addObject:paths];
lastPoint = newpoint;
[self setNeedsDisplay];
NSLog(#"%#",pathArray[0]);
}
}
else
{
return;
}
[super touchesMoved: touches withEvent: event];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [touches anyObject];
if ([touch type] == UITouchTypeStylus && drawable) //pencil touch
{
[pathEndPointArray addObject:tempEndPointArray];
}
if ([touch type] == UITouchTypeStylus && !drawable)
{
[self.delegate CacheLIView_showPopup_message:#"Already cupped!"];
}
[self touchesMoved:touches withEvent:event];
}
-(void)undo{
}
-(void)foward{
}
-(void)re_draw_after_rotate{ }
I need to create these function.

Answer 1

I would suggest the following (no code here):
create a second array pathUndoArray
Upon undo, remove the last entry from pathArray (if exists) and add it (at the end) to pathUndoArray, then redraw.
Upon redo, remove the last entry from pathUndoArray (if exists) and add it (at the end) to pathArray, then redraw.
Upon a new touch, you'll have to delete the pathUndoArray
You could also take a look at NSUndoManager.