I'm building a project and want to add a NSNumber into a NSDictionary. But the it crashed because of the null value. So, I created another small program to check what happened. As you can see in the snapshot: Why the the value of NSNumber in NSDictionary is null?
I've run your code and I could reproduce the problem. But it seems like a debugger problem. For instance, if after your dictionary is created, go to the console and try printing the dictionary.
po dictionary
My result is like:
$4 = 0x2083e770 {
number = 1;
}
So it's not null at all. Also, after that, anum is assigned correctly and b is set to YES. So it really looks like a debugger issue instead of a bug from you.
Related
What I am trying to do is convert a document to an dictionary and then iterate that dictionary to see what's inside, but I am having the following problem when trying to convert the document.
I have the following code:
CBLDocument *document = row.value;
NSDictionary *dict = document.properties;
the xCode is always complaining "[__NSCFDictionary currentRevision]: unrecognized selector sent to instance 0x90c4150" when running to the second statement.
I have also tried NSDictionary *dict = document.currentRevision.properties;
It's not working either.
Could anyone help me with that?
OK, it turns out row.value is not a document(is actually a dictionary), but nobody tells me that when I emit(#[somekey], doc); The doc (which is the value) is actually a dictionary instead of a document.
But weird though the compiler did not complain when assigning the dictionary to a CBLDocument.
I have a variable with an NSInteger type.. if I set a breakpoint on the variable and print it's output into the log, I get the expected value (ie 0).. however it looks very different on the debugger stacktrace variable list (180821440).. can someone explain what's going on?
I'm running Xcode 5.1.1 with Apple LLVM 5.1 having a None optimization level for the compiler
from the discussion of Martin R and Droppy above.. I figured out this was happening.
In the original code I was getting the taxiAmount value from an http call like so:
[serverGateway_ getTaxiAmountWithCoordinate:coordBlock onSuccessBlock:^(NSData *responseData)
{
[parser_ parseTaxiAmountWithData:responseData onSuccessBlock:^(NSNumber *taxiAmount)
{
[cityManager_ setTaxiAmount:taxiAmount];
so I was sending an NSNumber value to a NSInteger varialbe
- (void)setTaxiAmount:(NSInteger)taxiAmount
{
taxiAmount_ = taxiAmount;
}
in this case typing po taxiAmount returned 0, whereas p taxiAmount returned 180520272:
so what was causing this whole hoopala was treating a NSNumber as an NSInteger.. obviously correcting the line to
[cityManager_ setTaxiAmount:[taxiAmount integerValue]];
fixed the problem (and cleared the confusion)
I am keeping my data in a property called practiceRecords (an NSArray of dictionaries).
I check to see if the data already exists in the documents folder.
If yes, I load the data into self.practiceRecords.
If not, I build the array of dictionaries (using literal syntax), keeping this data in the self.practiceRecords property, and then write the data out to the documents folder.
(I am NOT reloading the data after writing it out)
As far as I am able to tell, there are no problems occurring during this process.
Then I have a step where I modify my data as follows ...
-(void)incNumberOfTriesFor:(NSString *)stringOfIndex {
if (self.practiceRecords)
{
int index = [stringOfIndex intValue];
int numberOfTries = [(NSNumber *)(self.practiceRecords[index][#"tries"]) intValue] + 1;
//CRASHING on this next line.
self.practiceRecords[index][#"tries"] = #(numberOfTries);
//message to helper method
[self writePracticeRecords];
}
}
So the first time through (when the array is built and written out) I get a crash at the indicated line.
The error is:
-[__NSDictionaryI setObject:forKeyedSubscript:]: unrecognized selector sent to instance
I quit the app, check the documents folder and see the data file written out with no issues.
I re-run the app, and then get no crash and the data file still looks great.
This is repeatable.
If the data file exists, no crash.
If the data first needs to be created, then a crash.
(In all cases, I manually look inside the resulting data file and see exactly what I expect to see - no issues there)
I'm not sure where to even begin squashing this bug, and would really like to understand the details of why this is happening.
Thanks very much for any help!
Just to recap the correct comments above:
-[__NSDictionaryI setObject:forKeyedSubscript:]: unrecognized selector sent to instance
NSDictionary does not implement any of the set... methods because it is immutable. You state that you're creating with literals syntax when the data is not found on disk. The literal syntax creates immutable containers
Instead, try...
// try to initialize from disk, but if not
// we can still use literal (immutable) syntax, but in a mutable container
self.practiceRecords = [NSMutableDictionary
dictionaryWithDictionary:#{ #"key" : #"value" }];
I have been attempting to debug a issue with my code, and just came upon an odd phenomenon. Found this in the debug area when a breakpoint was triggered:
Am I correct in observing that there are multiple values for this key: #"6898173"??
What are possible causes of this? I do not set those key-value pairs using the string literal, but by getting a substring of a string retrieved and decoded from a GKSession transmission.
I still have this up in the debug area in xcode, incase theres anything else there that might help.
EDIT:
By request, here is the code that would have created one of the two strings (another was created at an earlier time):
[carForPeerID setObject:[[MultiScreenRacerCarView alloc] initWithImage:[UIImage imageNamed:#"simple-travel-car-top_view"] trackNumber:[[[NSString stringWithUTF8String:data.bytes] substringWithRange:range] intValue]] forKey:[[NSString stringWithUTF8String:[data bytes]] substringFromIndex:9]];
The string in data might look something like this:
car00.0146898173
EDIT:
Code that sends the data:
[self.currentSession sendData:[[NSString stringWithFormat:#"car%i%#%#", [(MultiScreenRacerCarView *)[carForPeerID objectForKey:peerID] trackNumber], speed, [(MultiScreenRacerCarView *)[carForPeerID objectForKey:peerID] owner]] dataUsingEncoding:NSUTF8StringEncoding] toPeers:#[(NSString *)[peersInOrder objectAtIndex:(self.myOrderNumber + 1)]] withDataMode:GKSendDataReliable error:nil];
Sorry its hard to read. Its only one line.
What you're seeing is a debugger "feechure". When you have a mutable dictionary and modify it, the debugger may not show you the correct view of the object.
To reliably display the contents of an NSMutableArray or NSMutableDictionary, switch to the console and type po carForPeerID.
I am pulling data from the web that is formatted in JSON and when I parse the data using "ValueForKeyPath" it stores the string value as an id object.
So I store the data into a NSMutableArray
In the debugger window it shows all the elements added as (id) null.
I have an if statement
if ([[self.activeCategories objectAtIndex:selected] boolValue] == true)
Sometimes I would say 20% of the time it fails the if statement when it should not.
I was wondering if it was because the self.activeCategories is storing id types. Do I need to do [NSString stringWithFormat#"%#", x] to all the objects inside the array? It seems like when I just straight cast it by using (NSString *) it is still type id in the debugger.
It's a very strange error to me... as the error is not consistently reproducible.
Try it like that:
if ([[self.activeCategories objectAtIndex:selected] boolValue])
According to that article a BOOL may hold values other than 0 and 1 which may fail the comparison.