experience share in Nambu

1, 设置当前程序，使之可以自动运行. 

a) NSMutableArray loginItems = (NSMutableArray) CFPreferencesCopyValue((CFStringRef)
"AutoLaunchedApplicationDictionary", (CFStringRef) "loginwindow",
kCFPreferencesCurrentUser, kCFPreferencesAnyHost);
loginItems = [[loginItems autorelease] mutableCopy];
如此得到所有启动项，其中每个启动项都是个dictionary，启动项有2个key，分别是Hide(BOOL类型), Path(String类型)
b) 删除启动项则 [loginItems removeObject:anItem];
增加启动项则 [loginItems addObject:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO],"Hide", appPath, "Path", nil]];
注：appPath可以 = [[[NSBundle mainBundle] bundlePath] copy]
c) 最后，写回启动项去.
CFPreferencesSetValue((CFStringRef)
@"AutoLaunchedApplicationDictionary", loginItems, (CFStringRef)
@"loginwindow", kCFPreferencesCurrentUser, kCFPreferencesAnyHost);
CFPreferencesSynchronize((CFStringRef) @"loginwindow",
kCFPreferencesCurrentUser, kCFPreferencesAnyHost);

2, 窗口关闭之后，通过点击dock上的图标，再次显示一个窗口的做法.

- (BOOL)applicationShouldHandleReopen:(NSApplication )theApplication hasVisibleWindows:(BOOL)flag

{

if (flag) 
return NO;
else
{

return YES;

}

}

3, 像sql语句一样，限制返回结果的条数，用setFetchLimit

// get the objects of the entites according predicate and sortDescriptors and limit

+ (NSArray *)objectsEntityForName:(NSString *)entityName

forPredicate:(NSPredicate *)predicate
forSortDescriptors:(NSArray)sortDescriptors
limit:(NSInteger)limit

{

NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:[NBCoreData managedObjectContext]];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];

if(sortDescriptors)

NSArray *objects = [[NBCoreData managedObjectContext] executeFetchRequest:request error:nil]; }

return objects;

4, 高效的通知行高变化，如果你用[NSIndexSet indexSetWithIndexesInRange:0—rowsCount – 1]