UITableView reloadData crashes with error [__NSCFConstantString objectForKey:] - objective-c

Question

I am parsing data from server and display this data in my app. This data is a JSON data and it looks like this:
{"getMessages":[{"msgid":"1","message":"Hello.","dateposted":"2012-08-28"}]}
That's when a message is available to be sent, however, if no messages were available, JSON will look like this:
{"status":"No messages available"}
In my app, I use NSJSONSerialization to parse the JSON. Here is how I do it:
if ([data length] > 0)
{
NSDictionary *parsedData = [NSJSONSerialization JSONObjectWithData:data options
NSJSONReadingMutableContainers error:nil];
if (![parsedData objectForKey:#"getMessages"])
{
[self.messageArray addObject:#"No Messages"];
}
else
{
self.messageArray = (NSMutableArray *)[parsedData objectForKey:#"getMessages"];
}
}
As you can see, when the parsedData has no getMessages key, it will add the No Messages in
self.messageArray, but if it has the key, it will add the values related to it.
self.messageArray was the array I used to populate the messageTable. At the end of the download, I put the code [messageTable reloadData].
The problem is this: Reloading the table works if the parsedData contains the key getMessages. However, if the key was not found, reloading the table crashes.
This is my tableView:cellForRowAtIndexPath method:
NSString *tableIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:tableIdentifier];
if (cell == nil)
cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:tableIdentifier] autorelease];
if (tableView == messageTable) //I do this since there is another table I am using
{
NSString *string = [NSString stringWithFormat:#"%#", [self.messageArray objectAtIndex:0]];
if ([string isEqualToString:#"No Messages"])
{
cell.textLabel.text = string;
}
else
{
NSDictionary *dict = [self.messageArray objectAtIndex:indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:#"%#", [dict objectForKey:#"message"]];
}
}
In messageTable, I check first if the first index of self.messageArray is equal to the string "No Messages", this is to let the user know that no messages can be retrieved. If the
string is not equal, it will then assume that the data inside the array is a dictionary and therefore, it will be parsed to display the message.
After making use of breakpoints and logs, I realized that the crash happens while reloading the table. I inserted a breakpoint and a log at the start of the method tableView:cellForRowAtIndexPath but it never even got there. I tried checking the content of the self.messageArray and it does contain "No Messages".
The crash tells me this error: [__NSCFConstantString objectForKey:]: unrecognized selector sent to instance 0x10ed84
I know that this error is telling me that I am calling the method objectForKey in a NSString, but I really don't know why. Can anyone help me here?

Answer 1

try this
[self.messageArray removeAllObjects];
[self.messageArray addObject:[parsedData setObject:#"No Messages" forKey:#"getMessages"]];
mostly the dictionary is not setting for the key.. just check..
Also,
NSDictionary *diction = [self.messageArray objectAtIndex:0];
NSString *string = [NSString stringWithFormat:#"%#", [diction objectForKey:#"getMessages"]];
if ([string isEqualToString:#"No Messages"])
{
cell.textLabel.text = string;
}
else
{
NSDictionary *dict = [self.messageArray objectAtIndex:indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:#"%#", [dict objectForKey:#"message"]];
}

Answer 2

First make sure that messageArray is defined as NSMutableArray... and if you are reloading your parsedData from time to time then try this
if (![parsedData objectForKey:#"getMessages"])
{
[self.messageArray removeAllObjects];
[self.messageArray addObject:#"No Messages"];
}
else
{
[self.messageArray removeAllObjects];
self.messageArray = [[parsedData objectForKey:#"getMessages"] mutableCopy];
}