RBTreeManager is a set of classes built to easily manage hierarchical data in iOS TableViews. These classes were originally built because of a need to display threaded discussion posts (lots of them) in an iOS application. Unfortunately TableViews want there data in a flat format (i.e. array) but we all like to have our data reference it's parents/children so we can easily navigate it. So this was my solution.
To use the TreeMananger just copy the RBTreeManager.* and TreeNode.* files into your application somewhere. Once you have the files you can create a new RBTreeManager object, set its delegate, and start populating it:
_RBTreeManager = [[RBTreeManager alloc] init];
[_RBTreeManager setDelegate:self];
[_RBTreeManager beginUpdates];
for (int i = 0; i < 3; i++)
{
NSString *parentKey = [self genRandStringLength:10];
NSString *parent = parentKey;
[_RBTreeManager addObject:parent forKey:parentKey withComparator:^(id lhs, id rhs) {
return [((NSString *)lhs) compare:rhs ];
}];
int randomChildren = 1 + random() % 2;
for (int x = 0; x < randomChildren; x++)
{
NSString *childKey = [self genRandStringLength:10];
NSString *child = childKey;
[_RBTreeManager addObject:child forKey:childKey toParent:parentKey withComparator:^(id lhs, id rhs) {
return [((NSString *)lhs) compare:rhs ];
}];
}
}
[_RBTreeManager endUpdates];Next you need to implement the RBTreeManager delegate methods:
- (void)RBTreeManagerWillChangeContent:(RBTreeManager *)manager
{
[_tableView beginUpdates];
}
- (void)RBTreeManager:(RBTreeManager *)manager didChangeObject:(id)object atIndex:(int)index forChangeType:(RBTreeManagerChangeType)type newIndex:(int)newIndex
{
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:0];
NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:newIndex inSection:0];
switch (type) {
case RBTreeManagerChangeTypeInsert:
[_tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationTop];
break;
case RBTreeManagerChangeTypeDelete:
[_tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationTop];
break;
case RBTreeManagerChangeTypeMove:
[_tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationTop];
[_tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationTop];
break;
default:
break;
}
}
- (void)RBTreeManagerDidChangeContent:(RBTreeManager *)manager
{
[_tableView endUpdates];
}And finally your TableView delegate and datasource methods:
#pragma mark - TableView DataSource
- (void)configureCell:(UITableViewCell *)cell forIndex:(int)index
{
cell.textLabel.text = (NSString *)[_RBTreeManager objectAtIndex:index];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [_RBTreeManager count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = @"NodeCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:cellIdentifier] autorelease];
cell.indentationWidth = INDENTATION_WIDTH;
cell.autoresizesSubviews = YES;
cell.autoresizingMask = UIViewAutoresizingFlexibleWidth;
}
[self configureCell:cell forIndex:indexPath.row];
return cell;
}
#pragma mark - TableView Delegate
- (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath
{
return [_RBTreeManager depthOfObjectAtIndex:indexPath.row];
}Adds the supplied object to the root of the tree identified by the supplied key.
- (void)addObject:(id)object forKey:(id)key;Parameters
object
The object to add
key
The key used to identify this object
Discussion
This is the main entry point for objects into the root of the tree. Using this method will at the object at the end of the tree. If not called between a beginUpdates and endUpdates block, will cause RBTreeManager to rebuild.
Adds the supplied object to the root of the tree identified by the supplied key, places the object based on the sort block supplied
- (void)addObject:(id)object forKey:(id)key withComparator:(NSComparisonResult (^)(id, id))sortBlock;Parameters
object
The object to add
key
The key used to identify this object
sortBlock
Block that will be called to place this object into the correct order
Discussion
This is the main entry point for objects into the root of the tree when sorting of the objects is required. If not called between a beginUpdates and endUpdates block, will cause RBTreeManager to rebuild.
Adds the supplied object under the supplied parent identified by the supplied key
- (void)addObject:(id)object forKey:(id)key toParent:(id)parent;Parameters
object
The object to add
key
The key used to identify this object
Discussion
This is the main entry point for objects into the root of the given parent. Using this method will at the object at the end of the parents children. If not called between a beginUpdates and endUpdates block, will cause RBTreeManager to rebuild.
Adds the supplied object to the parent identified by the supplied key, places the object based on the sort block supplied
- (void)addObject:(id)object forKey:(id)key toParent:(id)parent withComparator:(NSComparisonResult (^)(id, id))sortBlock;Parameters
object
The object to add
key
The key used to identify this object
sortBlock
Block that will be called to place this object into the correct order
Discussion
This is the main entry point for objects into the parent when sorting of the objects is required. If not called between a beginUpdates and endUpdates block, will cause RBTreeManager to rebuild.
Removed the object with the specified key from the tree
- (void)removeObjectForKey:(id)key;Parameters
key
The key used to identify this object
Discussion
Removes the specified object. If not called between a beginUpdates and endUpdates block, will cause RBTreeManager to rebuild.
Returns the object at the given index
- (id)objectAtIndex:(int)index;Parameters
index
Integer value corresponding to an index of the flattened tree. Main use is to get the proper object for a UITableView.
Return Value
The object stored at the given index
Discussion
RBTreeManager flattens out a hierarcy of nodes for easy access and placement in a UITableView and this method allows us to get the proper node after flattening.
Returns the integer (0-based) depth of the object at the given index
- (int)depthOfObjectAtIndex:(int)index;Parameters
index
Integer value corresponding to an index of the flattened tree. Main use is to get the proper object for a UITableView.
Return Value
An integer representing the depth of the object at the given index
Discussion
Mainly used in the tableView:indentationLevelForRowAtIndexPath: UITableViewDelegate method for proper positioning
Returns the integer (0-based) depth of the object for the given key
- (int)depthOfObjectForKey:(id)key;Parameters
index
Integer value corresponding to an index of the flattened tree.
Return Value
An integer representing the depth of the object for the given key
Discussion
A way of getting the depth of an object when all you have is the key
Returns the integer count of all objects stored in the RBTreeManager
- (int)count;Discussion
Mainly used in the tableView:numberOfRowsInSection: UITableViewDatasource method so your table view knows how many rows it'll need to display
Tells the RBTreeManager that you will be doing alot of updates so it shouldn't rebuild the flattend view
- (void)beginUpdates;Discussion
Flattening out the tree is an expensive operation and so it shouldn't be done if you are doing alot of inserts at once
Tells the RBTreeManager that you've finished doing your bulk updates and that it's time to rebuild the flattend view
- (void)endUpdates;Discussion
Flattening out the tree is an expensive operation and so it shouldn't be done if you are doing alot of inserts at once
Called to inform the delegate that the RBTreeManager is going to change it's underlying data
- (void)treeManagerWillChangeContent:(RBTreeManager *)manager;Parameters
manager
The RBTreeManager that is preparing to change it's data
Discussion
You might want to inform you users that the data is changing, or stop the UI from updateing until the data is stable again
Called on every change to the underlying data
- (void)treeManager:(RBTreeManager *)manager didChangeObject:(id)object atIndex:(int)index forChangeType:(RBTreeManagerChangeType)type newIndex:(int)newIndex;Parameters
manager
The RBTreeManager that is preparing to change it's data
object
The Object that was changed
index
The original index of the changed object
newIndex
The new index of the object
Discussion
Want to update your UI as changes are happening, this is the method that will allow it
Called once the RBTreeManager has finished modifying it's underlying data
- (void)treeManagerDidChangeContent:(RBTreeManager *)manager;Parameters
manager
The RBTreeManager that just changed it's data
Discussion
Now that the RBTreeManager is done changing things you might want to update your UI
- Add more tests showing other aspects of RBTreeManager
- Implement breadth first navigation so that different types trees can be displayed.