I want to store in a NSMutableDictionary some null values using NSNull and then serialize this data using a property list. Problem is NSNull is not allowed and I get "Property list is in invalid format" error. Is there a workaround for this? Seems very surprising they didn't put NSNull on the list of valid plist objects.
I convert NSArray or NSDictionary to NSData before serializing. Following is a category on nsarray for serializing and deserializing. This comfortableby handles some data being nsnull
#implementation NSArray(Plist)
-(BOOL)writeToPlistFile:(NSString*)filename{
NSData * data = [NSKeyedArchiver archivedDataWithRootObject:self];
NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * documentsDirectory = [paths objectAtIndex:0];
NSString * path = [documentsDirectory stringByAppendingPathComponent:filename];
BOOL didWriteSuccessfull = [data writeToFile:path atomically:YES];
return didWriteSuccessfull;
}
+(NSArray*)readFromPlistFile:(NSString*)filename{
NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * documentsDirectory = [paths objectAtIndex:0];
NSString * path = [documentsDirectory stringByAppendingPathComponent:filename];
NSData * data = [NSData dataWithContentsOfFile:path];
return [NSKeyedUnarchiver unarchiveObjectWithData:data];
}
Instead of using a property list, consider using an NSKeyedArchiver and NSKeyedUnarchiver. Properties lists have a fixed set of types, and that doesn't include NSNull, and it isn't meant to be extended.
Here are links to the relevant documentation: NSCoding, NSKeyedArchiver and NSKeyedUnarchiver.
No, there is no way to put NSNull in a property list. (Trivia: the binary property list format actually supports nulls, but the writer doesn’t implement support.)
For a dictionary, the easiest workaround is to simply filter out the null values, so { foo = "bar"; baz = null; } becomes { foo = "bar"; }.
From the documentation of NSPropertyListSerializationClass:
A property list object. plist must be
a kind of NSData, NSString, NSNumber,
NSDate, NSArray, or NSDictionary
object. Container objects must also
contain only these kinds of objects.
So you need to have one of those. Depending on the type of data, you could put in a placeholder instead of NSNull and then do a process before/after loading the .plist (like, for example, using a zero-length NSData object to represent your NSNull in the plist). Exactly what kind of placeholder would be dependent on what kind of data you are storing, and choosing something to avoid. Then, after loading, translate the empty NSData back to NSNull.
Related
I am having problem with creating the Plist File that saves data received from web service using JSON. The Plist File cannot be created. The path is empty and data is saved to nowhere. This problem occurred when I cleaned the derived data. Please suggest any solution for this.
JSON data:
eventID = 2356;
eventName = "Testing Event";
This is how I save in Plist:
NSArray *eventsDictionary = [dataDictionary objectForKey:#"eventList"];
NSDictionary *plistDict = [NSDictionary dictionaryWithObject:eventsDictionary
forKey:#"Events"];
if ([eventsDictionary count]==0) {
NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
path = [path stringByAppendingPathComponent:DATA_DICTIONARY_KEY_USER_DEFAULTS];
[plistDict writeToFile:path atomically:YES];
}
else {
NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];
path = [path stringByAppendingPathComponent:DATA_DICTIONARY_KEY_USER_DEFAULTS];
[plistDict writeToFile:path atomically:YES];
}
Thank you very much.
You mentioned in a comment that the data was obtained from a web service as JSON and then converted to a dictionary.
The problem is almost certainly that your JSON data contains null values, which means that your dictionary contains instances of NSNull. You cannot write NSNull to a file like this because it is not one of the property list types. Writing a file like this only works with instances of NSDictionary, NSArray, NSString, NSData, NSNumber, and NSDate. Also any dictionary keys must be strings.
If there's an NSNull (or an instance of any non-property list class) then writing the file like this will fail.
You need to either go through the data and remove all NSNull instances, or else write your file some other way.
Here is the simplest way:
Add your dict to array:
NSMutableArray * mutArr = [NSMutableArray alloc]init];
[mutArr addObject:plistDict];
[self saveToPlistName:#"yourplist" fromArray:mutArr];
and use this method
-(void)saveToPlistName:(NSString *)plistName fromArray:(NSMutableArray*)array
{
NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentFolder = [path objectAtIndex:0];
NSString *filePath = [documentFolder stringByAppendingFormat:[NSString stringWithFormat:#"/%#.plist",plistName]];
[array writeToFile:filePath atomically:YES];
NSLog(#"SAVE SUCCESS TO DIRECTORY%#",filePath);
}
vote for me if its helpful for you
I'm loading a file to a NSMutableArray. I'm doing it like this:
if(!self.dataArray){
self.dataArray = [[NSMutableArray alloc] init];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES);
NSString *arrayPath = [[paths objectAtIndex:0]
stringByAppendingPathComponent:#"array.out"];
self.dataArray = [NSMutableArray arrayWithContentsOfFile:arrayPath];
}
The array that is loaded into the file consists of multiple NSDictionaries.
However, this somehow deallocates the array in the memory because when I log dataArray after doing this, it logs nil. How come?
Update
I've figured out that [NSMutableArray arrayWithContentsOfFile:arrayPath] is logging nil because the code in which I'm uploading the content to the file, doesn't create the file:
// write data to disk
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *arrayPath = [[paths objectAtIndex:0]stringByAppendingPathComponent:#"array.out"];
[self.dataArray writeToFile:arrayPath atomically:YES];
NSLog(#"uploaded file: %#", arrayPath); // logs an arrayPath, but one that doesn't exists.
Check the following,
Check the dataArray is a weak property ? If so, change to strong.
Check the file exists at path, using
[[NSFileManager defaultManager] fileExistsAtPath:arrayPath];
Verify the file have expected content, by logging it.
Confirm the File content is organized as a property list (plist). Verify it in plist editor/Xcode.
If you dynamically creating it, check the path you are writing to.
Confirm the method of writing NSArray to plist. Use
[array writeToFile:path atomically:YES];
Note:
If you are dynamically creating the file and you are testing on Simulator; you can
find the file by logging file path and following it on Finder.
Property List Reference
Apple documentation
Per Apple documentation, the array returns nil if the file can’t be opened or if the contents of the file can’t be parsed into an array.
Did you use the [writeToFile:atomically:] method to write the array to a file?
Also, make sure that the filePath string matches exactly on both write and read ends. I've wasted a lot of time trying to hunt down a bug when it turned out I had misspelled the name of the file or used the wrong file extension.
Another possibility: have you confirmed that this code is being executed? Sometimes I've had to change (!self.someProperty) to (self.someProperty != nil) in my if condition to get code like this to run.
Peter Segerblom and wildBillMunson are right: the array returns nil if the file can't be opened or if its content can't be parsed into an array.
You said "array.out" is an array of NSDictionaries. Whenever I have that set of data, I use the plist type of file and read it this way:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *directory = [paths objectAtIndex:0];
NSString *fullPath = [directory stringByAppendingPathComponent:#"data.plist"];
NSString *errorDesc = nil;
NSPropertyListFormat format;
NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:fullPath];
NSArray *data = (NSArray *)[NSPropertyListSerialization propertyListFromData:plistXML mutabilityOption:NSPropertyListMutableContainersAndLeaves format:&format errorDescription:&errorDesc];
Be sure to check if fullPath is not returning nil.
Hope this helps!
The development is in Xcode for iOS. I used 2 separate NSmutabledictionary.
I DON´T want to add them (when searching I found that often, but that is not what I try to do)
The app has to store them on the disk and when the app launches it can read the dictionary.
It is not a custom class so initWithCoder and the other one is not necessary (is this right?)
NSArray *data = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [data objectAtIndex:0];
path = [path stringByAppendingPathComponent:#"location"];
[NSKeyedArchiver archiveRootObject:"Dictionary" toFile:path];
This works but when I want to save another dictionary it won't work. My first thought would be to change the objectAtIndex to 1. But Xcode gives me an error when I do that. When I only give another name it simply won't save, but Xcode don't give an error.
What am I doing wrong?
// Find out where the documents folder is
NSString *documentsDirectory = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
// Create the file path for a file named 'location' inside the documents folder
NSString *path = [documentsDirectory stringByAppendingPathComponent:#"location"];
// Write an array containing both of your arrays to a file at that path
[NSKeyedArchiver archiveRootObject:#[myFirstArray, mySecondArray] toFile:path];
Then, to read them back:
// Read back the array containing the two arrays
NSArray *arrays = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
// Get the individual arrays from the array
NSMutableArray *myFirstArray = arrays[0];
NSMutableArray *mySecondArray = arrays[1];
How can I append values to an existing key in NSDictionary from a plist?
What I have is basically a plist saved in disc with a few keys and values, the keys are the names of some students with one initial value. What I’m trying to do that doesn't work is to append more items to existing keys/Students by reading the plist, adding it to a temporary NSDictionary, appending a temporary array to an existing key in the plist but when I save the plist back it doesn’t work, it only saves the last two items and basically deletes the initial value for that key.
Here is the code that I’m using…
- (IBAction)testing:(id)sender
{
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [dirPaths objectAtIndex:0];
NSString *fullPath = [documentsPath stringByAppendingPathComponent:#"studentsRecords.plist"];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:fullPath];
if(fileExists)
{
NSMutableDictionary *dictionaryRecords = [[NSMutableDictionary alloc]initWithContentsOfFile:fullPath];
NSLog(#"Items for Nathan: %#",[dictionaryRecords objectForKey:#"Nathan"]);// here the output is, Items for Nathan: Ruler
// which make sense since I only had one initial record for Nathan in my plist,
// Here, I want to add two more items to the key Nathan by appending an arry to
// NSMutableDictionary (dictionaryRecords) but it doesnt work
NSArray *tempArray = #[#"NoteBook", #"Pencil"];
[dictionaryRecords setObject:tempArray forKey:#"Nathan"];
[dictionaryRecords writeToFile:fullPath atomically:YES];
// when I check the plist after saving this, I only see the last two values, NoteBook and Pencil
// instead of the three that I'm expecting, Ruler, NoteBook and Pencil
}
}
What am I missing here?
Thanks a lot in advance.
[dictionaryRecords setObject:tempArray forKey:#"Nathan"] replaces whatever the previous value was with tempArray.
If you want to add to the existing array, you have to retrieve it, make a mutable copy, and append to it.
Here is how I made it work. I hope I didn't over complicated things here but for some reason I had to use two arrays, an NSArray and an NSMutableArray, I would think that the NSMutableArray would be enough but it didn't work.
- (IBAction)testing:(id)sender
{
// get directory path
NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [dirPaths objectAtIndex:0];
// create plist
NSString *fullPath = [documentsPath stringByAppendingPathComponent:#"studentsRecords.plist"];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:fullPath];
// if file exists create dictionary
if(fileExists)
{
// add items from plist to dictionary
NSDictionary *dictionaryExistingRecords = [[NSDictionary alloc]initWithContentsOfFile:fullPath];
// make a copy if dictinary with existing items
NSMutableDictionary *dictionaryNewRecords = [dictionaryExistingRecords mutableCopy];
// array to hold existing values from a spcecified key
NSArray *arrayWithExistingKey = [dictionaryExistingRecords objectForKey:#"Nathan"];
// mutable array to add existing and be able to insert new items
NSMutableArray *arrayOldAndNewItems = [NSMutableArray arrayWithArray:arrayWithExistingKey];
// insert new items to array
[arrayOldAndNewItems addObject:#"Snow Pans"];
// add old and new items to specified key
[dictionaryNewRecords setObject:arrayOldAndNewItems forKey:#"Nathan"];
// save new records to plist
[dictionaryNewRecords writeToFile:fullPath atomically:YES];
}
}
#end
I've got this wired problem, I cannot get the content from the file and initiate my NSMutableArray with it.
Here's my code:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSLog(#"Does file exist?: %i", [[NSFileManager defaultManager] fileExistsAtPath:[NSString stringWithFormat: #"%#/length.txt", documentsDirectory]]);
NSMutableArray *tempArr;
tempArr = [[NSMutableArray alloc] initWithContentsOfFile:[NSString stringWithFormat: #"%#/length.txt", documentsDirectory]];
When trying this, initWithContentsOfFile returns (null). The row checking if the file exist prints '1' to the console.
This is the code I'm using to save the data:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
[length.text writeToFile:[NSString stringWithFormat: #"%#/length.txt", documentsDirectory] atomically:NO];
I'm using more or less exactly the same code in a different program without problems.
Really need some help here, perhaps I'm just blind for the moment...
When you try to create an array from the contents of a file, the file must be in plist format, and the outer-most plist element must be <array>. If it doesn't have that format, initialization will fail and your array will be nil.
You're creating the file by writing an NSString to a file, which means you should probably be reading it in to an NSString, not an NSArray.
The docs for NSArray's initWithContentsOfFile: method say:
Return Value An array initialized to contain the contents of the file
specified by aPath or nil if the file
can’t be opened or the contents of the
file can’t be parsed into an array.
The returned object might be different
than the original receiver.
You don't include the declaration of length in your code snippet, but I'm guessing that length.text returns an NSString object, not an NSArray. So you'd need to read that back from a file using initWithContentsOfFile: from NSString, not NSArray.