NSString is being returned as 'null' - objective-c

I have this simple method for returning the file path. I am passing the file name as argument. Then when I call this method this method returns 'null' if running on device but works fine on simulator. Is there anything I am doing wrong?
-(NSString*) getFilePathForFile:(NSString*)fileName
{
NSArray *array = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [array objectAtIndex:0];
NSString *temp = [documentsDirectory stringByAppendingPathComponent:fileName];
return temp;
}
NSString *path = [self getFilePathForFile:#"settingInfo.plist"]
Any help would be appreciated.
Thanks

It sounds like some sort of memory management problem. Have you tried to use "Build and Analyze" to see if Xcode can pick up any memory problems?
Otherwise, try this and see if you get something non-null:
NSString *path = [[self getFilePathForFile:#"settingInfo.plist"] retain];

The only way that method can fail and not throw an exception is if the array returned by NSSearchPathForDirectoriesInDomains is nil. Check that a valid array is being returned.

Related

How to edit elements in plist file

I have a Settings.plist and I want to edit some values in this file.
My function to edit/writing is:
- (void) setParamWithName: (NSString*) Name withValue: (NSString*) Value {
// get paths from root direcory
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
// get documents path
NSString *documentsPath = [paths objectAtIndex:0];
// get the path to plist file
NSString *plistPath = [documentsPath stringByAppendingPathComponent:#"Settings.plist"];
// check to see if Data.plist exists in documents
if (![[NSFileManager defaultManager] fileExistsAtPath:plistPath])
{
// if not in documents, get property list from main bundle
plistPath = [[NSBundle mainBundle] pathForResource:#"Settings" ofType:#"plist"];
}
// read property list into memory as an NSData object
NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
NSString *errorDesc = nil;
NSPropertyListFormat format;
// convert static property list into dictionary object
NSDictionary *temp = (NSDictionary *)[NSPropertyListSerialization propertyListFromData:plistXML mutabilityOption:NSPropertyListMutableContainersAndLeaves format:&format errorDescription:&errorDesc];
if (!temp)
{
NSLog(#"Error reading plist: %#, format: %d", errorDesc, format);
}
// checking if element exists, if yes overwriting
// if element not exists adding new element
[temp writeToFile:plistPath atomically:YES];
}
This function read and write (with te same values) Settings.plist.
I do not have any idea (my knowledge about objective-c is not enough) how to add new element or edit existing element. Can anyone help mi with this issue?
I think it's easier as you think.
Once you got the path of the file read it into a NSDictionary. Make a mutable copy of that dictionary with mutableCopy and NSMutableDictionary.
Now edit that mutable dictionary as you like (add s.th., remove s.th., edit s.th. and so on).
Now that you're done you can write it back to the old path as you did with temp.
Your main problem is that you're not working with a mutable version of that dicitionary. It'd make your life much easier.

How to write data in .plist?

I'm trying to save some comments in a plist, that's OK cause its just a prototype. The problem is that i can read from plist but when I try to write and read after that, it throws an "array out of bounds" exception. I can't figure it out what I'm doing wrong here.
NSString *filePath = [[NSBundle mainBundle] pathForResource:#"Comments" ofType:#"plist"];
NSMutableArray *plistArray = [[NSMutableArray alloc] initWithContentsOfFile:filePath];
NSMutableDictionary *newComment = [NSMutableDictionary dictionary];
[newComment setValue:commentTitle.text forKey:#"title"];
[newComment setValue:comment forKey:#"comment"];
[plistArray addObject:newComment];
[plistArray writeToFile:filePath atomically:NO];
That works fine, then i try to read:
NSString *filePath = [[NSBundle mainBundle] pathForResource:#"Comments" ofType:#"plist"];
NSMutableArray *plistArray = [[NSMutableArray alloc] initWithContentsOfFile:filePath];
NSMutableDictionary *dictionary = (NSMutableDictionary *) [plistArray objectAtIndex:0];
NSLog(#"%#", [dictionary objectForKey:#"title"]);
And it throws the exception.
If I add the item manually to the plist, it works fine, i guess it means that my reading code its fine.
Could it be the structure of my plist?
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<array>
</array>
</plist>
* Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (1) beyond bounds (1)'
I added the "description" to the array before writing to the plist. If i use the following code:
NSString *aDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
// NSString *aFilePath = [NSString stringWithFormat:#"%#/Comments.plist", aDocumentsDirectory];
//
// NSMutableArray *plistArray = [[NSMutableArray alloc] initWithContentsOfFile:aFilePath];
The return is (null)
But if i use:
NSString *filePath = [[NSBundle mainBundle] pathForResource:#"Comments" ofType:#"plist"];
NSMutableArray *plistArray = [[NSMutableArray alloc] initWithContentsOfFile:filePath];
i can see the contents of the array, and its all working properly.
The problem is: In both ways i cant write to the file, it keeps returning "NO". And i already checked the permissions
You are trying to write the file into mainBundle. Definitely not possible.
You will have to write the plist file to Documents or Application Support folder of the app.
Create File Path in Documents Directory :
NSString *aDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *aFilePath = [NSString stringWithFormat:#"%#/Comments.plist", aDocumentsDirectory];
Write to FilePath
[plistArray writeToFile:aFilePath atomically:YES];
Read From FilePath
NSMutableArray *plistArray = [[NSMutableArray alloc] initWithContentsOfFile:aFilePath];
I see two problems with your code:
(May or may not be a problem). If the file does not exist initially, the initWithContentsOfFile: selector will return nil, causing the rest of your code to be no-ops.
(Probably the cause). You may not write to the bundle resources directory. Store your file in the Documents or Caches directory instead.
To locate your documents directory, use something like this:
- (NSString*) pathForDocument:(NSString*)documentName {
NSArray *documentDirectories = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
if(documentDirectories.count < 1) return nil;
return [[documentDirectories objectAtIndex:0] stringByAppendingPathComponent:documentName];
}
First of all, why are you writing a file into your bundle?
Then, to address your problem, check if you actually did write the file.
if ([plistArray writeToFile:filePath atomically:NO])
NSLog (#"Written");
else
NSLog (#"Not Written");
Also, log your array when you're read it using -(void)description to check the contents of the dictionary.
Edit
As you said that you're not writing to your plist. For now, just create a test plist on your desktop.
NSString *testPath = [[NSString stringWithString:#"~/Desktop/Comments.plist"] stringByExpandingTildeInPath];
if ([plistArray writeToFile:testPath atomically:NO])
NSLog (#"Written");
else
NSLog (#"Not Written");
If that still returns Not Written, then there's something wrong with your dictionary. Which I doubt because it's just strings (Though they could be placeholders for asking your question on stackoverflow. The docs states that the classes in the dictionary must be of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary). If that says written though, I'm guessing it doesn't write to your bundle because of permissions, which then you have to change your plist location to somewhere else other than your bundle, which I highly recommend.
If you only put one item in the array, you should obviously use index 0 instead of 1 when reading from it:
NSMutableDictionary *dictionary = (NSMutableDictionary *) [plistArray objectAtIndex:0];

can't save plist. path is not writable

I'm saving a lot of informations in a plist. This one is by standart in my mainBundle.
this is my method to load the path and the data from the plist. if the file in the "application support" folder doesn't exist, i'm copying it from the mainBundle to there.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
self.plistPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:#"%#.plist",plistName]];
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath: self.plistPath])
{
NSString *pathInBundle = [[NSBundle mainBundle] pathForResource:plistName ofType:#"plist"];
self.plist = [NSMutableDictionary dictionaryWithContentsOfFile:pathInBundle];
NSLog(#"plist doesnt exist");
}
else {
self.plist = [NSMutableDictionary dictionaryWithContentsOfFile:self.plistPath];
NSLog(#"plist exist");
}
NSLog(#"plist path: %#",self.plistPath);
if i add the following lines at the end, there's only NO the answer:
if([fileManager isWritableFileAtPath:self.plistPath]) NSLog(#"YES");
else NSLog(#"NO");
after all, i tried to save with [self.plist writeToFile:self.plistPath atomically:YES];, which is also not working.
sorry for answering so late - i had a lot of other stuff to do. back to my problem: i only get the error, when i try to add a new entry to my dictionary (plist). editing is no problem. i think the problem is, how i try to add the entry. my code looks like:
NSMutableDictionary *updateDict = [[self.plist objectForKey:#"comments"]mutableCopy];
NSMutableDictionary *tmpDict = [[[NSMutableDictionary alloc]init]autorelease];
[tmpDict setObject:comment forKey:#"comment"];
[tmpDict setObject:author forKey:#"author"];
[tmpDict setObject:car forKey:#"car"];
[tmpDict setObject:part forKey:#"part"];
[tmpDict setObject:date forKey:#"date"];
[updateDict setObject:tmpDict forKey:[NSNumber numberWithInt:[updateDict count]+1]];
[self.plist setObject:updateDict forKey:#"comments"];
if([self.plist writeToFile:self.plistPath atomically:YES]) {
return YES;
}
else {
return NO;
}
self.plist is my local copy of the file at plistPath. the structure of my plist looks like: https://img.skitch.com/20111026-tcjxp9ha4up8ggtfjy7ucgqcqe.png
hope this helps
Ok, so that's not the Documents directory and iOS doesn't have an Application Support directory created in the sandbox by default, which is why you can't write.
You can either change your method call to look-up the real documents directory:
NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
Or, after you get the path to the Application Support directory, you must check to see if it exists already and if not, create it.
please go through the previous post which shows the different way to copy the plist from mainBundle. Use [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error]; method instead.
Did you find answer? if not, you need to change this line:
[updateDict setObject:tmpDict forKey:[NSNumber numberWithInt:[updateDict count]+1]];
to
[updateDict setObject:tmpDict forKey:[NSString stringWithFormat:#"%d",[updateDict count]+1]];
Key name is string, not object.

Objective-C creating a text file with a string

I'm trying to create a text file with the contents of a string to my desktop. I'm not sure if I'm doing it right, I don't get errors but it doesn't work either...
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDesktopDirectory, NSUserDomainMask, YES);
NSString *desktopDirectory=[paths objectAtIndex:0];
NSString *filename = [desktopDirectory stringByAppendingString: #"file.txt"];
[myString writeToFile:filename atomically:YES encoding: NSUTF8StringEncoding error: NULL];
//Method writes a string to a text file
-(void) writeToTextFile{
//get the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
//make a file name to write the data to using the documents directory:
NSString *fileName = [NSString stringWithFormat:#"%#/textfile.txt",
documentsDirectory];
//create content - four lines of text
NSString *content = #"One\nTwo\nThree\nFour\nFive";
//save content to the documents directory
[content writeToFile:fileName
atomically:NO
encoding:NSStringEncodingConversionAllowLossy
error:nil];
}
You don't know if you're getting any errors because you're ignoring the returned YES/NO value of the -writeToFile:... method, and giving it no error pointer into which to record any possible failure. If the method returns NO, you'd check (and handle or present) the error to see what went wrong.
At a guess, the failure is due to the path you constructed. Try -stringByAppendingPathComponent: instead of -stringByAppendingString: ... this and its related methods properly handle paths.
The file probably is actually being created (ie, you might not be getting any errors after all). My guess is the file is created somewhere like "~/Desktopfile.txt" since your use of -stringByAppendingString: doesn't consider the string as slash-separated path. Check your home folder - I'll bet the file's there.
the problem is that the desktop directory string ends in nothing (no /). Check this out (on an iPhone) by using UIAlertview.

Reading data from a file

I'm new to mac and Cocoa so I'm sorry if this is a stupid question..
I need to read all the lines I wrote on a file I saved on my desktop.
The file format is .txt; I tried with stringWithContentsOfFile but the program freezes.
I tried with GDB and I noticed that, while the path is correct, the string which is supposed to contain the data returns nil.
Am I missing something important?
You need to use a path not just the filename
NSString *string;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
if ([paths count] != 0) {
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *newFile = [documentsDirectory stringByAppendingPathComponent:#"filename.txt"];
NSFileManager *fm = [NSFileManager defaultManager];
if ([fm fileExistsAtPath:newFile]) {
string = [NSString stringWithContentsOfFile:newFile];
}
}
You will need to replace the documents directory for the bundle directory if you are reading from there.
EDIT
I jumped the gun. It seems that this is NOT an iPhone question. None-the-less, you will need to pass in the full path, not just the filename