Issue with writing XMLDocument - objective-c

Question

I have a non doc-based app with table view with two columns, whose Value bindings are bound to two properties of the arrangedObjects of an array controller. I have a NSMutableArray in my AppDelegate that hold the data, as well as the corresponding #property and #synthesize. I implement key-value-coding accessor methods and use those when inserting data to the array in order to generate KVO notifications. I fill up my array with some NSDictionary objects from xml file. I've got all that working (modify, remove and add items), but what I'd like to do is write it back to xml file.
xmlData writeToFile:fileName atomically:YES
is writing to disk, but don't reflect changes when editing table view. There must be some tiny little thing I am forgetting. What is it?
Any suggestions would be very nice!
The code:
// AppDelegate.h
#import <Cocoa/Cocoa.h>
#interface AppDelegate : NSObject <NSApplicationDelegate>{
NSXMLDocument *xmlDoc;
NSXMLElement *root;
NSMutableArray *children;
}
#property (assign) IBOutlet NSWindow *window;
#property (nonatomic, copy)NSArray *children;
- (void)setChildren:(NSArray *)newChildren;
- (NSUInteger)countOfChildren;
- (id)objectInChildrenAtIndex:(NSUInteger)index;
- (void)insertObject:(id)object inChildrenAtIndex:(NSUInteger)index;
- (void)removeObjectFromChildrenAtIndex:(NSUInteger)index;
- (IBAction)addObject:(id)sender;
- (IBAction)saveXMLToFile:(id)sender;
- (void) populateTable;
#end
// AppDelegate.m
#import "AppDelegate.h"
#implementation AppDelegate
-(void) addObjectToChildren:(id)object{
[self insertObject:object inChildrenAtIndex:[self countOfChildren]];
}
#synthesize children;
- (id)init{
self = [super init];
if (self) {
children = [[NSMutableArray alloc] init];
}
return self;
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification{
[self populateTable];
}
#pragma mark - Indexed Accessors
- (void)setChildren:(NSArray *)newChildren{
if (children!=newChildren) {
children=[newChildren mutableCopy];
}
}
-(NSUInteger)countOfChildren{
return [self.children count];
}
-(id)objectInChildrenAtIndex:(NSUInteger)index{
return [self.children objectAtIndex:index];
}
- (void)insertObject:(id)object inChildrenAtIndex:(NSUInteger)index{
[children insertObject:object atIndex:index];
}
-(void)removeObjectFromChildrenAtIndex:(NSUInteger)index{
[children removeObjectAtIndex:index];
}
#pragma mark -
-(void)populateTable{
NSError *error=nil;
NSString *pathname = [#"~/myFile.xml" stringByExpandingTildeInPath];
NSURL *url = [NSURL fileURLWithPath:pathname];
xmlDoc = [[NSXMLDocument alloc] initWithContentsOfURL:url options:NSXMLDocumentTidyXML error:&error];
root = [xmlDoc rootElement];
NSArray *array=[root nodesForXPath:#"number" error:&error];
NSMutableArray *mArray=[[NSMutableArray alloc]init];
for (NSXMLElement *element in array) {
NSMutableDictionary *dict=[NSMutableDictionary dictionaryWithObjectsAndKeys:[element stringValue],#"id",#"number", #"name", nil];
[mArray addObject:dict];
}
[self setChildren:[NSArray arrayWithArray:mArray]];
}
#pragma mark - Actions
- (IBAction)addObject:(id)sender {
NSMutableDictionary *dict=[NSMutableDictionary dictionaryWithObjectsAndKeys:#"0",#"id",#"number", #"name", nil];
NSXMLElement *element=[[NSXMLElement alloc]initWithName:[dict objectForKey:#"name"] stringValue:[dict objectForKey:#"id"]];
[root insertChild:element atIndex:[self countOfChildren]];
[self addObjectToChildren:dict];
}
- (IBAction)saveXMLToFile:(id)sender {
NSString *fileName = [#"~/myFile.xml" stringByExpandingTildeInPath];
NSData *xmlData = [xmlDoc XMLDataWithOptions:NSXMLNodePrettyPrint];
if (![xmlData writeToFile:fileName atomically:YES]) {
NSBeep();
NSLog(#"Could not write document out...");
}
}
#end
The xml file:
<root>
<number>0</number>
<number>1</number>
<number>2</number>
<number>3</number>
<number>4</number>
<number>5</number>
</root>

Answer 1

When you change values in the tableview the underlying array is updated but not your XML document. You need to update your XML document or recreate it from the array to hold edited values.