iOS Slide out menu is causing app to crash. How to fix? - ios

Question

I am creating an rss feed app with a slide out navigation bar as shown here(http://www.appcoda.com/ios-programming-sidebar-navigation-menu/).
The app will load and RSS feeds will parse and appear on my main screen. You can click on a feed and it will lead to a webView to show that corresponding website. I will also have a navigation bar button on the top left to toggle the slide out menu. I am not able to proceed working on my app because it keeps crashing.BTW, I'm using a third party library called SWRevealViewController.Here is my MasterViewController:
//
// JSSMasterViewController.m
// News App
//
// Created by Steve on 4/5/14.
// Copyright (c) 2014 self.edu.steve. All rights reserved.
//
#import "JSSMasterViewController.h"
#import "JSSDetailViewController.h"
#import "SWRevealViewController.h"
#interface JSSMasterViewController () {
NSXMLParser *parser;
NSMutableArray *feeds;
NSMutableDictionary *item;
NSMutableString *title;
NSMutableString *link;
NSString *element;
}
#end
#implementation JSSMasterViewController
- (void)awakeFromNib
{
[super awakeFromNib];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
feeds = [[NSMutableArray alloc] init];
NSURL *url = [NSURL URLWithString:#"http://images.apple.com/main/rss/hotnews/hotnews.rss"];
parser = [[NSXMLParser alloc] initWithContentsOfURL:url];
[parser setDelegate:self];
[parser setShouldResolveExternalEntities:NO];
[parser parse];
// Change button color
_sidebarButton.tintColor = [UIColor colorWithWhite:0.96f alpha:0.2f];
// Set the side bar button action. When it's tapped, it'll show up the sidebar.
_sidebarButton.target = self.revealViewController;
_sidebarButton.action = #selector(revealToggle:);
// Set the gesture
[self.view addGestureRecognizer:self.revealViewController.panGestureRecognizer];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Table View
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return feeds.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
cell.textLabel.text = [[feeds objectAtIndex:indexPath.row] objectForKey: #"title"];
return cell;
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {
element = elementName;
if ([element isEqualToString:#"item"]) {
item = [[NSMutableDictionary alloc] init];
title = [[NSMutableString alloc] init];
link = [[NSMutableString alloc] init];
}
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
if ([elementName isEqualToString:#"item"]) {
[item setObject:title forKey:#"title"];
[item setObject:link forKey:#"link"];
[feeds addObject:[item copy]];
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
if ([element isEqualToString:#"title"]) {
[title appendString:string];
} else if ([element isEqualToString:#"link"]) {
[link appendString:string];
}
}
- (void)parserDidEndDocument:(NSXMLParser *)parser {
[self.tableView reloadData];
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if ([[segue identifier] isEqualToString:#"showDetail"]) {
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
NSString *string = [feeds[indexPath.row] objectForKey: #"link"];
[[segue destinationViewController] setUrl:string];
}
}
#end
Here is SideBar View controller that manages the Slide out menu:
//
// JSSSidebarViewController.m
// News App
//
// Created by Steve on 4/5/14.
// Copyright (c) 2014 self.edu.steve. All rights reserved.
//
#import "JSSSidebarViewController.h"
#import "SWRevealViewController.h"
#interface JSSSidebarViewController ()
#end
#implementation JSSSidebarViewController{
NSArray *menuItems;
}
- (id)initWithStyle:(UITableViewStyle)style
{
self = [super initWithStyle:style];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
menuItems = #[#"title", #"news", #"comments", #"map", #"calendar", #"wishlist", #"bookmark", #"tag"];
// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return [menuItems count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier = [menuItems objectAtIndex:indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
return cell;
}
- (void) prepareForSegue: (UIStoryboardSegue *) segue sender: (id) sender
{
// Set the title of navigation bar by using the menu items
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
UINavigationController *destViewController = (UINavigationController*)segue.destinationViewController;
destViewController.title = [[menuItems objectAtIndex:indexPath.row] capitalizedString];
// Set the photo if it navigates to the PhotoView
if ( [segue isKindOfClass: [SWRevealViewControllerSegue class]] ) {
SWRevealViewControllerSegue *swSegue = (SWRevealViewControllerSegue*) segue;
swSegue.performBlock = ^(SWRevealViewControllerSegue* rvc_segue, UIViewController* svc, UIViewController* dvc) {
UINavigationController* navController = (UINavigationController*)self.revealViewController.frontViewController;
[navController setViewControllers: #[dvc] animated: NO ];
[self.revealViewController setFrontViewPosition: FrontViewPositionLeft animated: YES];
};
}
}
#end
I am not able to find out the solution. Here is my logs:
2014-04-05 20:17:43.843 News App[4496:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
*** First throw call stack:
(
0 CoreFoundation 0x0000000101968495 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x00000001016c799e objc_exception_throw + 43
2 CoreFoundation 0x000000010191f374 -[__NSArrayM insertObject:atIndex:] + 820
3 UIKit 0x00000001002d40da -[UIView(UIViewGestures) addGestureRecognizer:] + 199
4 News App 0x0000000100001ecf -[JSSMasterViewController viewDidLoad] + 719
5 UIKit 0x000000010036a59e -[UIViewController loadViewIfRequired] + 562
6 UIKit 0x000000010036a777 -[UIViewController view] + 29
7 UIKit 0x00000001006752e2 -[UIClientRotationContext initWithClient:toOrientation:duration:andWindow:] + 390
8 UIKit 0x00000001002b0ffa -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] + 1109
9 UIKit 0x00000001002b0b9f -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:] + 36
10 UIKit 0x00000001002b0aef -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] + 101
11 UIKit 0x00000001002afdfe -[UIWindow _updateToInterfaceOrientation:duration:force:] + 377
12 UIKit 0x000000010036e70a -[UIViewController _tryBecomeRootViewControllerInWindow:] + 147
13 UIKit 0x00000001002aab1b -[UIWindow addRootViewControllerViewIfPossible] + 490
14 UIKit 0x00000001002aac70 -[UIWindow _setHidden:forced:] + 282
15 UIKit 0x00000001002b3ffa -[UIWindow makeKeyAndVisible] + 51
16 UIKit 0x000000010026fc98 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1788
17 UIKit 0x0000000100273a0c -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 660
18 UIKit 0x0000000100284d4c -[UIApplication handleEvent:withNewEvent:] + 3189
19 UIKit 0x0000000100285216 -[UIApplication sendEvent:] + 79
20 UIKit 0x0000000100275086 _UIApplicationHandleEvent + 578
21 GraphicsServices 0x0000000103ae171a _PurpleEventCallback + 762
22 GraphicsServices 0x0000000103ae11e1 PurpleEventCallback + 35
23 CoreFoundation 0x00000001018ea679 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 41
24 CoreFoundation 0x00000001018ea44e __CFRunLoopDoSource1 + 478
25 CoreFoundation 0x0000000101913903 __CFRunLoopRun + 1939
26 CoreFoundation 0x0000000101912d83 CFRunLoopRunSpecific + 467
27 UIKit 0x00000001002732e1 -[UIApplication _run] + 609
28 UIKit 0x0000000100274e33 UIApplicationMain + 1010
29 News App 0x0000000100002c23 main + 115
30 libdyld.dylib 0x00000001020005fd start + 1
31 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
Thank you for any Help!

Answer 1

The error is exactly what your error log says:
'*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'
You are trying to insert an object to an array and that object is nil. In this particular case, it's this line that's causing problem:
[self.view addGestureRecognizer:self.revealViewController.panGestureRecognizer];
You will need to alloc self.revealViewController.panGestureRecognizer first before adding it as the view's gesture recognizers.
One way to alloc the gesture recognizer:
UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(someMethod:)];
[self.view addGestureRecognizer:gestureRecognizer];