I'm getting an NSDictionary from JSON (using SBJson), and I want to store it. I'm using
[liveData writeToFile:localFilePath atomically:YES]
and it fails. The data looks like its all NSString, NSDictionary, and NSArray (which "atomically:YES" demands). I used the same localFilePath elesewhere.
So my question is: how can I find out where the problem is? What tools can I use to understand why writeToFile fails? The log doesn't show an error message.
It may have multiple reasons:
The path you are writing to is wrong, not writable (you don't have write access to it), or the parent directory does not exists (if localFilePath is "/path/to/file.plist" but the directory "/path/to/" does not exists, it will fail)
The liveData dictionary does contains objects that are not PropertyList objects. Only NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary objects can be written into a Property List file (and writeToFile:atomically: do write to a plist file so the dictionary do have to contains only PList objects for that method to succeed)
I know this is a 2 year old question. But since I just had this same problem and fixed it here's what I found. I bet your NSDictionary has some keys that are not NSStrings.
Instead of keying like:
[_myDictionay setObject:thisObj forKey:[NSNumber numberWithInt:keyNumber]];
Key like:
[_myDictionay setObject:thisObj forKey:[NSString stringWithFormat:#"%i",numberWithInt:keyNumber]];
That fixed my problem right up.
The top way can't be saved to a plist file.
Since you're getting your info from a JSON conversion, it is possible that there are some objects or keys that are NSNumbers in there. You would have to convert them. But that's a pain.
So since you already have it in json, just store it as the json string in its entirety in a #"data" key and the re-expand it when you load the plist later back into your array or dict.
I've tried saving an NSDictionary to disk with only numbers for keys and values. Switching the keys to NSString works but not when they keys are NSNumber. Do keys have to be NSString?
EDIT: I know better now that it can be any object that responds to hash; often it's NSString's, though.
Old thread : But this apple thread would be nice to read. Basically iOS has issue in Cache directory. For 1000+ folders it returns error.
I would suggest to add your own atomic mechanism to write file as a fallback.
https://developer.apple.com/forums/thread/128927
Related
I have a Class for handling my data in my project, and now I need to store the data.
I'd like to use a Plist but I'm a bit unsure of how to start.
My class is pretty simple - 6 pieces of data, flat (no hierarchy).
I want my app to start with no data, so can I assume that I should create the PList programmatically once the User creates their first piece of data? (That is, don't create a .plist file in 'Supporting Files' prior to distribution?)
Then, when the app starts the next time, read the data and create an NSMUtableArray array of Class instances?
To create a property list, all you need to do is use appropriate types (i.e. those that support the property list format: NSData, NSString, NSDictionary, NSNumber, NSDate, NSArray), store them in a single container, and tell the containing object to write itself to a file. To read the data, you can initialize that same type using a path. For example:
// writing some data to a property list
NSString *somePath = ... // replace ... with the path where you want to store the plist file
NSMutableDictionary myDict = [NSMutableDictionary dictionary];
[myDict setObject:#"Caleb" forKey:#"name"];
[myDict setObject:[NSNumber numberWithInt:240] forKey:#"cholesterolOrIQ"];
[myDict writeToFile:somePath atomically:YES];
// reading the file again
NSDictionary *readDict = [NSDictionary dictionaryWithContentsOfFile:somePath];
The simplest way is to simple save an NSArray or NSDictionary to disk. Caleb's answer goes into detail there so I won't repeat it, other than to say you might have to convert a non-compatible object like NSColor to an property list object like NSData. It's up to you to do this each time you save or load your data.
NSKeyedArchiver and NSKeyedUnarchiver give you a little more control over the process, but work pretty much the same way. You provide (or get back) a plist compatible root object (usually an NSDictionary) that contains your data. I recommend creating a dictionary that includes your data structure as well as an arbitrary number (your app's build number is a good choice) to use as a version indicator. This way if you ever update your data model you can easily determine if you need to do anything to convert it to the new version.
If you're putting your own objects into the data file, look into NSCoding. The protocol gives you two methods using NSKeyedArchiver and NSKeyedUnarchiver to save and restore your data. This is by far the most straightforward approach if your data model consists of anything more than a few simple strings and numbers, since you're dealing with your own native objects. In your case, you would have your data class implement NSCoding and use the NSKeyedArchiver and NSKeyedUnarchiver methods to encode your six instance variables. When it's time to save or load, pack the instance of your class into an NSDictionary (along with a versioning number as I mentioned above) and call NSKeyedArchiver's archiveRootObject:toFile:. Your save an load methods deal only with your own data object, which makes things easy for you. The common pitfall to watch out for here is if your custom data object contains other custom object. This is fine, but you have to make sure every object that's going to be saved has its own NSCoding implementation.
Two things you can do:
Use NSUserDefaults:
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html
The objectForKey method is the one you want to use to store your class. But, as pointed out in the comments, this shouldn't really be used for storing lots of user data; it's best for saving preferences.
For storing more data, you might want to look at Core Data. It's more complex, but should be better suited to your needs. Here's a tutorial on it:
http://mobile.tutsplus.com/tutorials/iphone/iphone-core-data/
Neither of these seems best for your simple application, but I leave this answer up since it gives alternatives for saving data to the iPhone.
I would like to save the content of a NSMutableDictionary object to a file. How do I do this ? I already know how to do this task with a NSDictionary object but I don't know how to convert/copy this NSMutableDictionary to a NSDictionary...unless there's a method to write directly the content of NSMutableDictionary to a file...I stress that the NSMutableDictionary object contains objects of NSDictionary type.
Thx for helping,
Stephane
NSMutableDictionary is a subclass of NSDictionary: you can use it anywhere you'd use NSDictionary. Literally, just pass the object through to the same code you use for NSDictionary right now.
In a more general sense, if you ever actually need to get a truly immutable NSDictionary from an NSMutableDictionary, just call copy on the NSMutableDictionary.
Other approaches include [NSDictionary dictionaryWithDictionary:] or [NSDictionary alloc] initWithDictionary:], which all amount to essentially the same thing.
If you just swing over to the NSDictionary documents. You will see there is a method for saving a dictionary to a file
writeToFile:atomically:
Writes a property list representation of the contents of the dictionary to a given path.
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
Parameters
path:
The path at which to write the file.
If path contains a tilde (~) character, you must expand it with stringByExpandingTildeInPath before invoking this method.
flag:
A flag that specifies whether the file should be written atomically.
If flag is YES, the dictionary is written to an auxiliary file, and then the auxiliary file is renamed to path. If flag is NO, the dictionary is written directly to path. The YES option guarantees that path, if it exists at all, won’t be corrupted even if the system should crash during writing.
Return Value
YES if the file is written successfully, otherwise NO.
This method recursively validates that all the contained objects are property list objects (instances of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary) before writing out the file, and returns NO if all the objects are not property list objects, since the resultant file would not be a valid property list.
If the dictionary’s contents are all property list objects, the file written by this method can be used to initialize a new dictionary with the class method dictionaryWithContentsOfFile: or the instance method initWithContentsOfFile:.
So the piece of code you are looking for is probably something like:
[myDict writeToFile:path atomically:YES]
where myDict is the dictionary you have and path is the path to the location you want to save it to
the code below is working, but I want to make sure it's correct. I'm nervous about having an empty Array inside my dictionary that I create from the plist, since typically it seems that if you don't, say, initWithCapacity:1 then you often get memory errors once you start trying to add items.
At least, that's been my experience with NSMutableDictionary. However, this is the first time I'm trying to implement nested data objects, so perhaps the reason this code works is that the nested array is automatically initialized when it's imported as part of its parent dictionary?
Any and all comments appreciated. Thanks.
First, here's what the plist looks like that I'm using to create my dictionary:
Next, here's my code where I'm using the plist to create a dictionary, then adding an item to dataArray
// Create a pointer to a dictionary
NSMutableDictionary *dictionary;
// Read "SomeData.plist" from application bundle
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *finalPath = [path stringByAppendingPathComponent:#"SomeData.plist"];
dictionary = [NSMutableDictionary dictionaryWithContentsOfFile:finalPath];
// Now let's see if we can successfully add an item to the end of this empty nested array. How 'bout the number 23
NSNumber *yetAnotherNumber = [NSNumber numberWithInt:23];
[[dictionary objectForKey:#"dataArray"] addObject:yetAnotherNumber];
// Dump the contents of the dictionary to the console
NSLog(#"%#", dictionary);
Okay, fine, simple, good. When I Log the dictionary contents it shows that "23" has been added as an array value to dataArray. So the code works. But again, I want to confirm that I'm not "getting lucky" here, with my code just happening to work even though I'm not properly initializing that nested array. If so, then I could run into unanticipated errors later on.
So to sum up, dataArray is an empty array inside the .plist, so do I need to initialize it somehow (using, for example initWithCapacity: or something else) before I can properly populate it, or is the way I'm coding here just fine?
Thanks again.
EDIT
Hey all. I've been doing continued research on this, in the interests of finding a satisfying answer. I think I may have stumbled upon something, via this link on deep copying. His previous posts on deep copying had presented some code to do essentially what I was looking for above: create a mutable copy of a dictionary or array, from a plist, that also has mutable sub-structures.
However, as mentioned in the link above, it looks like these methods were superfluous, due to the CFPropertyListCreateDeepCopy method, which can be invoked with a call such as
testData = CFPropertyListCreateDeepCopy(kCFAllocatorDefault, [NSDictionary dictionaryWithContentsOfFile:path], kCFPropertyListMutableContainersAndLeaves);
So, my question is, can I properly use CFPropertyListCreateDeepCopy, in the way shown, to achieve what I've been asking about here? In other words, can I use this method to import my dictionary from a plist with fully mutable, nested data objects?
As I mentioned in one of the comments, I know I can create a nested, mutable dictionary manually, but for complex data that's just not practical, and it seems unlikely that built-in methods to import a mutable plist don't exist. So, based on the above, it looks like I've possibly found the solution, but I'm still too new to this to be able to say for sure. Please advise.
(Side note: I would simply test the code, but as we've established, the current SDK is buggy with regard to allow you to edit immutable nested dictionaries, contrary to the documented behavior. So as before, I'm not just interested in whether this works, but whether it's correct)
Thanks in advance.
init... methods should only be called once, immediately after a call to alloc or allocWithZone:. When framework code creates and returns an object or graph of objects, their init... methods have already been called, so sending another init... message would have undefined results. Don't do that.
Interestingly, in spite of what the documentation appears to say (and admittedly I probably missed a key sentence or paragraph somewhere), when you create an instance of a mutable collection by reading a plist, any nested collections are also mutable. I ran the following little experiment in a test harness just to be sure:
NSMutableDictionary *pets = [NSMutableDictionary dictionaryWithContentsOfFile:#"/tmp/Pets.plist"];
NSMutableArray *cats = [pets objectForKey:#"cats"];
[cats addObject:#"Foo"]; // EDIT: Added line I accidentally omitted earlier
NSLog(#"%#", cats);
So again, the nested collections created when you read in the plist are fully initialized, and mutable to boot, so you can simply use them, as you've been doing.
EDIT
However, after doing some further reading of the docs, I think the OP is right to feel uneasy about relying on what is apparently an undocumented feature of the current version of the SDK. For example, the Property List Programming Guide states:
If you load the property list with
this call:
NSMutableArray * ma = [NSMutableArray arrayWithContentsOfFile:xmlFile];
ma is a mutable array with immutable
dictionaries in each element. Each key
and each value in each dictionary are
immutable.
So, to be on the safe side, if you need a nested collection to be mutable, you should create it yourself. For example, I'd recommend rewriting the code in the example above as follows:
NSMutableDictionary *pets = [NSMutableDictionary dictionaryWithContentsOfFile:#"/tmp/Pets.plist"];
NSArray *cats = [pets objectForKey:#"cats"];
NSMutableArray *mutableCats = [cats mutableCopy];
[pets setObject:mutableCats forKey:cats];
[mutableCats release];
You can then safely make changes to the nested mutable collection:
[mutableCats addObject:#"Foo"];
Any object in a dictionary which is created by reading from disk will be properly initialized. You will not have to do it on your own. However, as pointed out by jlehr, contents of the dictionary should be immutable. If you want the contents of the dictionary to be mutable, you will need to change them on your own. I have no idea why your program is not throwing an exception.
I do not know why you are getting memory errors while not using initWithCapacity:1 in other situations. The following code is perfectly valid:
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:#"object1"];
[array addObject:#"object2"];
NSLog(#"%#",array);
[array release];
If you don't specify a capacity, the array won't pre-allocate any memory, but it will allocate memory as required later.
Edit:
It is perfectly acceptable to use NSDictionary with CFPropertyListCreateDeepCopy. In Core Foundation, a CFPropertyList can be a CFDictionary, CFArray, CFNumber, CFString, or CFData. Since NSDictionary is toll-free bridged to CFDictionary, you can use it wherever a CFDictionary is asked for by casting, and vice-versa. Your code as is will give a warning, but you can suppress it by casting the dictionary and return values.
NSDictionary *testData = (NSDictionary*)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFDictionaryRef)[NSDictionary dictionaryWithContentsOfFile:path], kCFPropertyListMutableContainersAndLeaves);
I feel a little dumbfounded. I know how to store any kind of "plist supporting" data in a preferences file, such as NSArray, NSDictionary, NSString and their CF counterparts. No problem there.
Now I like to store the values of my custom object this way. I had thought that if I implement some kind of serialization/archiving protocol, I could get NSUserDefaults to understand my class just like it understand NSDictionary.
E.g, implementing the NSCoding protocol should give the NSUserDefaults code all that it needs: I give it the key names along with the values as plist compatible types (NSString, mostly in my case). But my encoder doesn't even get invoked. :(
Then I thought that there must be at least some function that generates a NSDictionary from the NSCoding protocol, so that I can then send this dict to store in the prefs. Ideally, there'd by something like the NSKeyedArchiver that I pass any NSCoding compatible object and it gives me a NSDictionary, and vice versa. But that doesn't appeat to exist in Apple's framework.
Do I have to write that really myself? I'd expect this would be a quite common need.
Note: I realize that NSKeyedArchiver generates a binary plist, which I could write as a plist file. But that's not what I want. I want to add the contents of this object to my app's prefs plist file, i.e. I want to store both my object and other prefs data in the plist file. That's what doesn't seem to be possible with the given functions.
I'm currently just adding objects to an NSDictionary then calling NSDictionary's "writeToFile:atomically:" method. I'm mostly adding strings, and an image as NSData, but I believe anything I add to the NSDictionary that implements the NSCoding protocol should get written to the file.
Then later when I call NSDictionary's initWithContentsOfFile everything gets put back in the dictionary as it had been. Would this work for you - letting the dictionary take care of the serialization stuff?
Some kind of serialization available in iPhone OS? Is that practically possible or should I quickly forget about that?
I am making a tiny app that stores some inputs in an NSMutableArray. When the user leaves, the inputs should stay alive until he/she returns to continue adding or removing stuff to/from that array.
When the app quits, there must be some way to store all the stuff in the array in a file. Or must I iterate over it, rip everything out and write it i.e. comma-separated somewhere, then the next time go in again, read the stuff in, and iterate over the lines in the file to make an array with that data? That would be hard like a brick. How to?
The easy way, since you already have an NSArray object is to write the array to disk using
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
and read it back in with:
- (id)initWithContentsOfFile:(NSString *)aPath
or
+ (id)arrayWithContentsOfFile:(NSString *)aPath
You can also use NSCoder.
You can probably search sof for the right code.
So long as the objects in the array implement NSCoding (NSString and NSValue do; if you're storing your own objects it's relatively straightforward), you can use:
[NSKeyedArchiver archiveRootObject: array toFile: filePath];
to save and:
array = [NSKeyedUnarchiver unarchiveObjectWithFile: filePath];
to load.
You can similarly load/save to NSData.
The iPhone SDK is designed to store data using SQLite tables.
You can use NSPropertyListSeralization, since NSArray is a type of property list. You can find more information here.