No known class method for selector 'defaultStore' - objective-c

Question

Am working my through the Big Nerd Ranch iOS Programming 3rd edition, and have run into a problem with the selector 'defaultStore' which is a singleton. The error says that there is no such class method, and I don't know how to fix the problem, which I have commented out.
I believe that there is a part where the book will switch over to Core Data, but I haven't reached that part yet.
ItemsViewController.m
#import "ItemsViewController.h"
#import "BNRItemStore.h"
#import "BNRItem.h"
#implementation ItemsViewController
- (id)init
{
// Call the superclass's designated initializer
self = [super initWithStyle:UITableViewStyleGrouped];
if (self) {
UINavigationItem *n = [self navigationItem];
[n setTitle:#"Homepwner"];
// Create a new bar button item that will send
// addNewItem: to ItemsViewController
UIBarButtonItem *bbi = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemAdd
target:self
action:#selector(addNewItem:)];
// Set this bar button item as the right item in the navigationItem
[[self navigationItem] setRightBarButtonItem:bbi];
[[self navigationItem] setLeftBarButtonItem:[self editButtonItem]];
}
return self;
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[[self tableView] reloadData];
}
- (IBAction)addNewItem:(id)sender
{
// Create a new BNRItem and add it to the store
BNRItem *newItem = [[BNRItemStore defaultStore] createItem];//No known class method for selector 'defaultStore'
// Incompatible pointer types initializing 'BNRItem*__strong' with an expression of 'NSArray'
// Figure out where that item is in the array
int lastRow = [[[BNRItemStore defaultStore] allItems] indexOfObject:newItem]; //No known class method for selector 'defaultStore'
NSIndexPath *ip = [NSIndexPath indexPathForRow:lastRow inSection:0];
// Insert this new row into the table.
[[self tableView] insertRowsAtIndexPaths:[NSArray arrayWithObject:ip]
withRowAnimation:UITableViewRowAnimationTop];
}
- (id)initWithStyle:(UITableViewStyle)style
{
return [self init];
}
- (void)tableView:(UITableView *)tableView
moveRowAtIndexPath:(NSIndexPath *)fromIndexPath
toIndexPath:(NSIndexPath *)toIndexPath
{
[[BNRItemStore defaultStore] moveItemAtIndex:[fromIndexPath row] //No known class method for selector 'defaultStore'
toIndex:[toIndexPath row]];
}
- (void)tableView:(UITableView *)aTableView
didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
DetailViewController *detailViewController = [[DetailViewController alloc] init];
NSArray *items = [[BNRItemStore defaultStore] allItems];//No known class method for selector 'defaultStore'
BNRItem *selectedItem = [items objectAtIndex:[indexPath row]];
// Give detail view controller a pointer to the item object in row
[detailViewController setItem:selectedItem];
// Push it onto the top of the navigation controller's stack
[[self navigationController] pushViewController:detailViewController
animated:YES];
}
- (void)tableView:(UITableView *)tableView
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath
{
// If the table view is asking to commit a delete command...
if (editingStyle == UITableViewCellEditingStyleDelete)
{
BNRItemStore *ps = [BNRItemStore defaultStore];//No known class method for selector 'defaultStore'
NSArray *items = [ps allItems];
BNRItem *p = [items objectAtIndex:[indexPath row]];
[ps removeItem:p];
// We also remove that row from the table view with an animation
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
}
}
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
{
return [[[BNRItemStore defaultStore] allItems] count];//No known class method for selector 'defaultStore'
}
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Create an instance of UITableViewCell, with default appearance
// Check for a reusable cell first, use that if it exists
UITableViewCell *cell =
[tableView dequeueReusableCellWithIdentifier:#"UITableViewCell"];
// If there is no reusable cell of this type, create a new one
if (!cell) {
cell = [[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:#"UITableViewCell"];
}
// Set the text on the cell with the description of the item
// that is at the nth index of items, where n = row this cell
// will appear in on the tableview
BNRItem *p = [[[BNRItemStore defaultStore] allItems]//No known class method for selector 'defaultStore'
objectAtIndex:[indexPath row]];
[[cell textLabel] setText:[p description]];
return cell;
}
#end
BNRItemStore.h
#import "BNRItemStore.h"
#import "BNRItem.h"
#implementation BNRItemStore
+ (BNRItemStore *)defaultStore
{
static BNRItemStore *defaultStore = nil;
if(!defaultStore)
defaultStore = [[super allocWithZone:nil] init];
return defaultStore;
}
+ (id)allocWithZone:(NSZone *)zone
{
return [self defaultStore];
}
- (id)init
{
self = [super init];
if(self) {
allItems = [[NSMutableArray alloc] init];
}
return self;
}
- (void)removeItem:(BNRItem *)p
{
[allItems removeObjectIdenticalTo:p];
}
- (NSArray *)allItems
{
return allItems;
}
- (void)moveItemAtIndex:(int)from
toIndex:(int)to
{
if (from == to) {
return;
}
// Get pointer to object being moved so we can re-insert it
BNRItem *p = [allItems objectAtIndex:from];
// Remove p from array
[allItems removeObjectAtIndex:from];
// Insert p in array at new location
[allItems insertObject:p atIndex:to];
}
- (BNRItem *)createItem
{
BNRItem *p = [BNRItem randomItem];
[allItems addObject:p];
return p;
}
BNRItemStore.m
#import "BNRItemStore.h"
#import "BNRItem.h"
#implementation BNRItemStore
+ (BNRItemStore *)defaultStore
{
static BNRItemStore *defaultStore = nil;
if(!defaultStore)
defaultStore = [[super allocWithZone:nil] init];
return defaultStore;
}
+ (id)allocWithZone:(NSZone *)zone
{
return [self defaultStore];
}
- (id)init
{
self = [super init];
if(self) {
allItems = [[NSMutableArray alloc] init];
}
return self;
}
- (void)removeItem:(BNRItem *)p
{
[allItems removeObjectIdenticalTo:p];
}
- (NSArray *)allItems
{
return allItems;
}
- (void)moveItemAtIndex:(int)from
toIndex:(int)to
{
if (from == to) {
return;
}
// Get pointer to object being moved so we can re-insert it
BNRItem *p = [allItems objectAtIndex:from];
// Remove p from array
[allItems removeObjectAtIndex:from];
// Insert p in array at new location
[allItems insertObject:p atIndex:to];
}
- (BNRItem *)createItem
{
BNRItem *p = [BNRItem randomItem];
[allItems addObject:p];
return p;
}
#end

Answer 1

Make sure that the #interface block for BNRItemStore (in BNRItemStore.h) declares that method:
#interface BNRItemStore : NSObject
+ (BNRItemStore *)defaultStore;
// etc.
#end
The compiler looks at the interface to know what methods are available on that class.