Not Able to show UIAlert on Exception - ios

Question

I am using UITableView. And if there is no network connection then there will be exception thrown in viewDidload. My viewDidLoad function is:
#try {
NSLog(#"Request URL = %#",URLString);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL
URLWithString:URLString]];
NSData *response = [NSURLConnection sendSynchronousRequest:request
returningResponse:nil error:nil];
NSError *jsonParsingError = nil;
NSDictionary *tableData = [NSJSONSerialization JSONObjectWithData:response
options:0
error:&jsonParsingError];
// Grab whole data with data field in JSON
// responseArray = [tableData objectForKey:#"data"];
responseArray = [[NSMutableArray alloc]initWithArray:[tableData objectForKey:#"data"]];
for(int i = 0; i < responseArray.count; i++)
{
NSArray * tempArray = responseArray[i];
responseArray[i] = [tempArray mutableCopy];
}
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
[btn setFrame:CGRectMake(280.0, 0.0, 40.0, 40.0)];
[btn setImage:[UIImage imageNamed:#"sort_icon.png"] forState:UIControlStateNormal];
[btn addTarget:self action:#selector(showActionSheet) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *barbutton = [[UIBarButtonItem alloc]initWithCustomView:btn];
self.navigationItem.rightBarButtonItem = barbutton;
}
#catch (NSException *exception)
{
exceptionOccured = YES;
NSLog(#"Exception Ocurred");
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Error in connectivity" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
In cellForRowAtIndexPath I am doing this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
#try {
NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
tempDict = [responseArray objectAtIndex:indexPath.row];
return cell;
}
#catch (NSException *exception)
{
NSLog(#"Error in CEll Create");
NSLog(#"Draw Alert");
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Error in connectivity" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
}
and in AlertViewDelegate Function I am doing
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
[self.navigationController popViewControllerAnimated:YES];
}
Now problem is that it is not showing the Alert whenever there is an exception and re-throws the exception and shows the Error
Thread 1: EXC_BAD_ACCESS(code=2, address=0x2)
Any help will be appreciated...

Answer 1

You should avoid throwing exceptions in your code.
First of all you could use Reachability Class to determine whether or not an active internet connection is available.
I would definitively recommend using the NSURLConnectionDelegate protocol for URL connections. So you can use the better asynchronous programming style.

Answer 2

The problem is somewhere else. When - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath is called it means the system needs the tableView to be reloaded. Therefore, you should not check for data inside that function. When you enter this function, you should be sure that your data is ok.
What you have to do is firstly check your data in a specific function:
-(void)CheckData(NSArray *responseArray) {
#try {
//Retrieve your data & check if its valid
self.dataArray = responseArray;
[self.tableView reloadData];
}
#catch (NSException *exception)
{
NSLog(#"Error in check Data");
NSLog(#"Draw Alert");
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Error in connectivity" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
Then, implement your data source delegates:
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [self.dataArray count];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = (UITableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil){
cell = [[[UITableViewCell alloc]initWithStyle:UITableViewStylePlain reuseIdentifier:CellIdentifier] autorelease] ;
}
//TODO: Init your cell using your self.dataArray content
return cell;
}

Answer 3

I would recommend import this SystemConfiguration framework and use the same. This will check whether network connection is available or not. Below is the simple code:-
#import <SystemConfiguration/SystemConfiguration.h>
-(void)yourMethod
{
SCNetworkConnectionFlags flags = 0;
if (yourhostname && [yourhostname length] > 0)
{
flags = 0;
BOOL found = NO;
SCNetworkReachabilityRef reachabilityRef = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, [yourhostname UTF8String]);
if (reachabilityRef)
{
found = SCNetworkReachabilityGetFlags(reachabilityRef, &flags)
&& (flags & kSCNetworkFlagsReachable)
&& !(flags & kSCNetworkFlagsConnectionRequired);
CFRelease(reachabilityRef);
reachabilityRef = NULL;
}
if (found)
{
NSLog(#"Connection available");
}
else
{
NSLog(#"Connection not available");
}
}