Drag View from the point you touch it iPhone - iphone

Question

I know how to drag a view or object:
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [[event allTouches] anyObject];
if( [touch view] == ViewMain)
{
CGPoint location = [touch locationInView:self.view];
ViewMain.center = location;
}
}
but I would like to start dragging that view or image from the point where I touched it. for example if I drag (I highlighted the view and placed blue on the cursor):
the moment I start dragging if I drag the mouse 20 px to the right for example then I would like the view to also drag 20 px instead of:
maybe I have to change the center of the view to the point where I fist touch it. How could I do that?
In other words I would like to do something like when you drag the apps on the iPad:

Answer 1

float startX = 0;
float startY = 0;
-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches] anyObject];
if( [touch view] == ViewMain)
{
CGPoint location = [touch locationInView:self.view];
startX = location.x - ViewMain.center.x;
startY = ViewMain.center.y;
}
}
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [[event allTouches] anyObject];
if( [touch view] == ViewMain)
{
CGPoint location = [touch locationInView:self.view];
location.x =location.x - startX;
location.y = startY;
ViewMain.center = location;
}
}