Graphics Programs Reference
In-Depth Information
@end
In
TouchDrawView.m
, set every completed line's
containingArray
property in
endTouches:
.
- (void)endTouches:(NSSet *)touches
{
for (UITouch *t in touches) {
NSValue *key = [NSValue valueWithNonretainedObject:t];
Line *line = [linesInProcess objectForKey:key];
if (line) {
[completeLines addObject:line];
[linesInProcess removeObjectForKey:key];
[line setContainingArray:completeLines];
}
}
[self setNeedsDisplay];
}
Finally, in
clearAll
of
TouchDrawView.m
, comment out the code that removes all
of the objects from the
completeLines
and create a new instance of
NSMutableAr-
ray
instead.
- (void)clearAll
{
[linesInProcess removeAllObjects];
// [completeLines removeAllObjects];
completeLines = [[NSMutableArray alloc] init];
[self setNeedsDisplay];
}
Build and profile the application. Choose
Leaks
as the instrument to use.
Draw a few lines and then double tap the screen to clear it. Select the
Leaks
instrument
from the top left table and wait a few seconds. Three items will appear in the summary
table: an
NSMutableArray
, a few
Line
instances, and a
Malloc 16 Bytes
block. This
memory has been leaked.
Select the
Leaks
pop-up button in the breadcrumb bar and change it to
Cycles & Roots
(
Figure 21.19
)
. This view gives you a lovely graphical representation of the retain cycle:
an
NSMutableArray
(our
completeLines
array) has a reference to a list of
Line
s,
and each
Line
has a reference back to its
containingArray
.
Figure 21.19 Cycles and Roots
