Fastest way to check for descendants of an object
Fastest way to check for descendants of an object
- Subject: Fastest way to check for descendants of an object
- From: Keith Blount <email@hidden>
- Date: Tue, 27 Apr 2010 08:33:06 -0700 (PDT)
Hello,
I have a model object that represents a single node in a tree (it can be used in an NSOutlineView for instance). As such, it has a "children" NSMutableArray iVar which can store other objects of the same class, which in turn may have their own children.
E.g:
@interface MyNode : NSObject
{
NSMutableArray *children;
}
@end
Whereby "children" would contain instances of MyNode which in turn have "children" that may contain other instances of MyNode (obviously the above is just a grossly simplified version of my actual class which does much more).
There are occasions when I need to check if one node object is the descendant of another node object. My current code for this is as follows:
- (BOOL)isDescendantOfOrOneOfNodes:(NSArray*)nodes
{
// Returns YES if we are contained anywhere inside the array passed in, including inside sub-nodes.
NSEnumerator *enumerator = [nodes objectEnumerator];
id node = nil;
while (node = [enumerator nextObject])
{
if (node == self) return YES; // Found ourself
// Check all sub-nodes
if ([[node children] count] > 0)
{
if([selfisDescendantOfOrOneOfNodes:[node children]])
returnYES;
}
}
// Didn't find self inside any of the nodes passed in
returnNO;
}
- (BOOL)isDescendantOfNodes:(NSArray*)nodes
{
// Returns YES if any node in the array passed in is an ancestor of ours.
NSEnumerator *enumerator = [nodes objectEnumerator];
id node = nil;
while (node = [enumerator nextObject])
{
// Note that the only difference between this and isAnywhereInsideChildrenOfNodes: is that we don't check
// to see if we are actually one of the items in the array passed in, only if we are one of their descendants.
// Check sub-nodes
if ([[node children] count] > 0)
{
if([selfisDescendantOfOrOneOfNodes:[node children]])
returnYES;
}
}
// Didn't find self inside any of the nodes passed in
returnNO;
}
So, in use, e.g:
if ([firstNode isDescendantOfOneOfNodes:[NSArray arrayWithObject:secondNode]])
// ... do something (e.g. prevent secondNode from being added as a child of firstNode).
My question is simply, is there a faster way of doing this? There are occasions when I need to run through and check potentially thousands of nodes each with thousands of descendants, and in this situation these checks can be quite time-consuming and slow things down. I know 10.5 introduced fast enumeration (e.g. "for (id node in nodes)"), and the only reason I'm not using that is that I need to support 10.4 too (I tested it and fast enumeration does speed things up a little, but not as much as I need at the volumes I'm talking about). So I'm just wondering if there is anything in the above that can be optimised to be faster. If not, I probably just need to re-examine where I'm calling these methods again, but I figured I'd start with first principles and initially check to see if there is any obvious quicker way of checking that an object is a descendant of another in the above situation that I might be missing.
Thanks and all the best,
Keith
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