I get the dictionary from web service and this dictionary contain encoded key-value pair. I used some code for decode this key-value.
Code no. 1 :
[NSString stringWithUTF8String:[[dict valueForKey:#"desc"] cStringUsingEncoding:[NSString defaultCStringEncoding]]];
But when I run this code then it get crashed and got the error [NSString stringWithUTF8String:]: NULL cString'
When debugging it, dictionary contain keys & values also "desc" key having a value.
On other side i have one code that worked fine.
Code no. 2:
[NSString stringWithFormat:#"%#",[dict valueForKey:#"desc"]];
But almost everywhere in my app, I used code no.1 and its worked very well.
and now i have totally confuse i this error [NSString stringWithUTF8String:]: NULL cString' came while i check dictionary contain keys & values.
Why do you create a C-String from NSString and then (back) NSString from C-String?
Why not simply
NSString *desc = dict[#"desc"];
And – as always – do not use valueForKey unless you can explain why you explicitly need KVC.
Related
I am using GDataXMLDocument. I need to parse very simple XML string. When I try to init XML with string I receive error:
-[myObj dataUsingEncoding:]: unrecognized selector sent to instance 0x7afb5690
My string is:
<rootNode>
<detail1>value</detail1>
<detail2>value</detail2>
<detail3>value</detail3>
<detail4>value</detail4>
</rootNode>
The line of the error is:
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
where I need to encode my string no NSData, so I can init my parser with it.
I suppose the problem is in NSUTF8StringEncoding, but I can not understand why!
I am using ARC with NON ARC for GDataXML set in compilation options.
How to solve this?
P.S. I have a remark which might be important. I receive an array from SOAP service. I used sudzc.com tool to create my classes. The SOAP service send to me array of structures. When I receive data using po command see what is inside and I decided that it consists of NSArray with XML sting inside. In general I extract each element of an array and try to parse it as XML to extract data I need.
May be I am wrong and that is the reason for that error.
I don't know why but I fix it casting once again to NSString with format using:
NSString *properStr = [NSString stringWithFormat:#"%#", str];
I am not sure why I need this, but it is wotking now.
I have an NSMutableDictionary that loads data from a certain source.
He is loading fine and while debugging i am sure he is loading and that in the end he has the exact number of elements. I also can see the elements as they should while debugging.
I just want to get the value of the the row having the key value = 3 .
I tried NSString * myString = [myMutabDict objectForKey:#"3"], considering that the value is in string ,and i followed it with the debugger, and i am sure that my NSDictionary has elements in it , and i can see them while debugging, and i can see the key 3 , but i still get null as an output …
What am i missing?
If you are sure you see a value with a key of 3 and you can't load it using the key #"3" then it is possible that the key is a number. Use:
NSString *myString = [myMutableDict objectForKey:#3];
or modern syntax:
NSString *myString = myMutableDict[#3];
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 have a NSMutableDictionary holding EXIF metadata from a picture.
An example:
const CFStringRef kCGImagePropertyExifExposureTime;
Instead of accessing every key individually, I just want write the whole dictionary content into a label.
When I want to write this data into the console I would just use:
NSLog(#"EXIF Dic Properties: %#",EXIFDictionary );
That works fine, but if I use:
NSString *EXIFString = [NSString stringWithFormat:(#"EXIF Properties: %#", EXIFDictionary)];
I get warnings that the result is not a string literally and if I try to use that string to set my label.text, the program crashes.
Any idea where my error is?
[NSString stringWithFormat:(#"EXIF Properties: %#", EXIFDictionary)] is not, as you may think, a method with two arguments. It's a method with one argument. That one argument is (#"EXIF Properties: %#", EXIFDictionary), which uses the comma operator and ends up returning EXIFDictionary. So in essence you have
[NSString stringWithFormat:EXIFDictionary]
which is obviously wrong. This is also why you're getting a warning. That warning tells you that the format argument is not a string literal, because using variables as format strings is a common source of bugs. But more importantly here, that argument isn't even a string at all, and so it crashes.
Remove the parentheses and everything will be fine. That will look like
[NSString stringWithFormat:#"EXIF Properties: %#", EXIFDictionary];
I get warnings that the result is not a string literally
Nah. You get a warning saying that the format string of stringWithFormat: is not a string literal. That's because you don't know how the comma operator (and a variadic function) works (that's why one should master the C language before trying to make an iOS app). Basically what you have here:
[NSString stringWithFormat:(#"EXIF Properties: %#", EXIFDictionary)]
is, due the behavior of the comma operator, is equivalent to
[NSString stringWithFormat:EXIFDictionary]
which is obviously wrong. Omit the parentheses, and it will be fine:
[NSString stringWithFormat:#"EXIF Properties: %#", EXIFDictionary]
You don't want those parentheses:
NSString *EXIFString = [NSString stringWithFormat:#"EXIF Properties: %#", EXIFDictionary];
I have an NSURLRequest being made that to a server that returns a string.
string = [[NSMutableString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
receivedData is the mutable array that the downloaded data is stored in. Everything works fine.
I have now, however, added another value to that string. An example of the returned string would be 14587728000000 , 376.99. Originally it was one value so I didn't have to do any splicing. But, now that I have another value, I want to be able to separate it into two different strings.
What should I do to separate the two values into different string? Some kind of search that goes till the first space, or something like that. I have access to the server, and the string is generated in PHP so the separator can be anything.
You can do this with the NSString componentsSeparatedByString method:
NSString *string = #"14587728000000,376.99";
NSArray *chunks = [string componentsSeparatedByString: #","];
You can find some other common NSString tricks (where I found this one) here.
Use -(NSArray *)componentsSeparatedByString: and pass in the token to split by.