so here's my function
+ (void) AddAddress:(NSString*)ip:(NSString*)mac {
NSMutableDictionary* currentAddresses = [[NSMutableDictionary alloc] initWithContentsOfFile:[self filePath:ADDRESSES_FILE]];
[currentAddresses setObject:mac forKey:ip];
[Configuration Write:currentAddresses];
[currentAddresses release];
}
[self filePath:ADDRESSES_FILE] returns a string containing the full path of a file (ADDRESSES_FILE) located in the Documents. The file may not exist, in this case I want to just write an object to the dictionary and then write it down
the problem is that when i do setObject forKey it doesn't add anything to the dict (if i just do alloc init to the dict, it works fine, but i want to read the records from the file, if there are any, and replace/add a record by using the AddAddress function)
First thing first, you'd rather respect naming convention of ObjC to be more easily understood... For instance, method names start with a small case and it's better to put a descriptive name before the colons for each arguments, a method name like that: AddAddress:: isn't really good...
Now, about loading a dictionary from a file, the thing is that if the file can't be loaded (doesn't exist, wrong format,...), the returned object will be nil, the simplest way to correct that is to put:
if(currentAddresses == nil) currentAddresses = [[NSMutableDictionary alloc] init];
Related
I currently have a three dimensional NSMutableArray which I need to deep copy. However, it appears that the following code causes it and its contents to become immutable, since it causes NSInvalidArgumentException when I attempt to remove any objects from it.
NSMutableArray* copy = [[[NSMutableArray alloc] initWithArray:input copyItems:YES] autorelease];
How can I deep copy an array without causing it to become immutable?
From the listing,
The copy imlementation of immutable classes usually returns the same
object - because it's immutable there is no need to have a "real"
copy. But you don't have to worry about this.
above from http://lists.apple.com/archives/cocoa-dev/2008/May/msg00172.html
So make sure before you add your input array, convert that input array into a mutable copy and then call the method.
Code:
NSMutableArray* mutableInput = [input mutableCopy];
NSMutableArray* copy = [[[NSMutableArray alloc] initWithArray:mutableInput copyItems:YES]autorelease];
Use NSCoding
in .h file
#interface classname : NSObject
in .m file
(id)copyWithZone:(NSZone *)zone
{
}
I create two NSMutableDictionary: dictionary1 and dictionary2. In the first dictionary I store some array object having there keys. And in the second dictionary I store the object of first dictionary with the key like this:
int page = 1;
[dictionary2 setObject:dictionary1 forKey:[NSString stringWithFormat:#"%d",page]];
[dictionary1 removeAllObjects];
but at the time of retrieve of the object i do like this
dictionary1 = [dictionary2 valueForKey:[NSString stringWithFormat:#"%d",page]];
NSLog(#"dictionary1 %#", dictionary1);`
Then it gives null value. I don't know what mistake I do.
After you add dictionary1 to dictionary2, you are removing all of the objects.
This is the same dictionary that is in dictionary2 (it does not create a copy), therefore you are removing the objects from it as well.
You need to remove the line [dictionary1 removeAllObjects];.
Then, since you are done with dictionary1 at this point, you can either remove the reference to it or set to a nice new shiny dictionary which is ready to use:
// Remove the reference
dictionary1 = nil;
// Or, create a new, empty dictionary
dictionary1 = [[NSDictionary alloc] init];
Did you correctly alloc/init dictionary1 and dictionary2? Make sure the dictionaries themselves are not nil.
try this
dictionary1 = [dictionary2 objectForKey:[NSString stringWithFormat:#"%d",page]];
In the Beginning iPhone 4 book, the author has this code to create a category for creating a deep copy of an NSDictionary that has an NSArray of names for each letter of the alphabet to show an example of an indexed table with a search bar.
#import "NSDictionary-MutableDeepCopy.h"
#implementation NSDictionary (MutableDeepCopy)
- (NSMutableDictionary *) mutableDeepCopy {
NSMutableDictionary *returnDict = [[NSMutableDictionary alloc] initWithCapacity:[self count]];
NSArray *keys = [self allKeys];
for (id key in keys) {
id oneValue = [self valueForKey:key];
id oneCopy = nil;
if ([oneValue respondsToSelector:#selector(mutableDeepCopy)]) oneCopy = [oneValue mutableDeepCopy];
else if ([oneValue respondsToSelector:#selector(mutableCopy)]) oneCopy = [oneValue mutableCopy];
if (oneCopy == nil)
oneCopy = [oneValue copy];
[returnDict setValue:oneCopy forKey:key];
[oneCopy release];
}
return returnDict;
}
#end
Can someone explain the for loop logic? I'm not sure what he's trying to do in seeing which value responds to which selector, and why it would be added to the dictionary. Thanks.
So, the for loop simply iterates through all the keys in the dictionary. Beforehand, we create a new dictionary called returnDict - this will be what we return.
For each key in the dictionary we want to copy, we...
Get the object stored for that key ([self valueForKey:key]), and save it into a variable called oneValue.
If oneValue implements our mutableDeepCopy method (ie, it's an NSDictionary) go call it, and assign the return value into a variable called oneCopy.
Else, we see if oneCopy implements the mutableCopy method. If it does, we put the output into the oneCopy variable.
At this point, we check to see if following steps (2) and (3) the oneCopy variable has had anything assigned to it (if (oneCopy == nil)). If it doesn't (ie, it's equal to nil) we can assume the object doesn't implement either mutableDeepCopy or mutableCopy, so we instead call a plain old copy and assign its value to oneCopy.
Add oneCopy into our returnDict dictionary using the original key.
That's the for loop - at the end of it all, we go and return the copied dictionary.
The logic in the for-loop is convoluted because the author is trying to get as mutable and as deep a copy of the entire array as possible. The code tries three different ways to satisfy this, in order of preference:
Use mutableDeepCopy if possible (if the object understands that message).
Otherwise, use mutableCopy if possible.
If all else fails, just use copy.
If the object is just plain not copiable, your code goes boom when it sends the object -copy, since no test is made for whether the object responds to -copy. This is appropriate, since trying to deep copy an array containing items that cannot be copied is definitely programmer error.
I am trying to convert (or copy?) a NSString into a NSMutableArray. I guess my problem is that I don't really understand the structure of a MutableArray. In my limited knowledge, an Array could look like this:
NoteBook = [[NSMutableArray alloc] init];
for (int temp = 0; temp < 3; temp++) {
[NoteBook insertObject:#"Page" atIndex:temp];
}
Which would give me an Array of PagePagePage. Let's assume I wanted to open a txt file which contains PagePagePage, but the words were separated by a defined string so that I can keep the individual objects in my array apart, like so: Page--- end of page ---Page--- end of page ---Page.
Now, my next step would be to read this information from the txt file:
NSString *tempTextOut = [NSString stringWithContentsOfFile:filePath
encoding:NSUTF8StringEncoding
error:&error];
NoteBook = [tempTextOut componentsSeparatedByString: #"\n--- end of page ---\n"];
However, the last line does not work and I'm told by xCode: Incompatible Objective-C types assigning 'struct NSArray*', expected 'struct NSMutableArray*'. I don't really understand this - NSArray and MutableArray should be compatible (as one is the subclass of the other). Shouldn't xCode tell me that the problem is that I've been trying to convert a NSString into an NSMutableArray?
Would I perhaps need to re-set my MutableArray before putting something back into it, because right now, it still contains PagePagePage which I have assigned to it in the first step. I thought my NoteBook mutable array would simply be replaced by the string, but I guess that won't be the case.
I'd very much appreciate any help in this matter. Thanks!
componentsSeparatedByString: returns a plain immutable NSArray, not an NSMutableArray. You can pass the array to [NSMutableArray arrayWithArray:] or use mutableCopy on the array to get a mutable array from it, or you can use addObjectsFromArray: on an existing NSMutableArray to add objects to it.
If you go the mutableCopy route, do remember that you are responsible for calling release or autorelease on it.
Assigning a mutable object to the same immutable type will lead to runtime errors if you want to manipulate the immutable instance.
You can get your mutable copy by calling:
NoteBook = [[tempTextOut componentsSeparatedByString: #"\n--- end of page ---\n"] mutableCopy];
If NoteBook is a retained property you should assign to it this way:
self.NoteBook = [[[tempTextOut componentsSeparatedByString: #"\n--- end of page ---\n"] mutableCopy] autorelease];
so the mutable copy doesn't get over retained. You can release in your dealloc method then as normal.
I'm having trouble in writing mutable dictionary to a file. Here's the code that I'm writing.
I'm reading the file like below: (first time when app is ran, it won't have any data)
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
self.favSaveFilePath = [[NSString alloc] initWithString:[documentsDirectory stringByAppendingPathComponent:#"Favorites.plist"]];
if([fm fileExistsAtPath:favSaveFilePath])
{
favoriteJokesDictionary = [[NSMutableDictionary alloc] initWithContentsOfFile:self.favSaveFilePath];
favoriteJokes = [[NSMutableArray alloc] initWithArray:[self.favoriteJokesDictionary objectForKey:#"FavoriteJokes"]];
return;
}
I'm adding new dictionary to array as below:
-(BOOL)addJokeToFavorite:(NSDictionary*)joke
{
BOOL success = NO;
[self.favoriteJokes addObject:joke];
success = [self.favoriteJokesDictionary writeToFile:self.favSaveFilePath atomically:YES];
return success;
}
I don't know why its not wring the dictionary to file. Can any one point me the mistake that I'm doing?
The Cocoa API is very specific about what kind of values can legally be in a dictionary when it is written out to file. One particular limitation that has been known to cause problems and which is not thoroughly discussed in the official API documentation is that all of the keys in your dictionary must be of type NSString (and your values must be one of NSData, NSDate, NSNumber, NSString, NSArray, or NSDictionary), even though the dictionary itself supports keys and values of any object type.
The reason for this restriction has to do with the fact that the dictionary gets stored as an XML document (or "property-list", in Apple-speak) by default. So I'd recommend verifying that your dictionary meets the requirements to be saved to file, and restructuring it if it doesn't.
Or, if restructuring your dictionary is not feasible, you might want to take a look at the NSKeyedArchiver class instead.
Looks like your favoriteJokesDictionary doesn't exist at all when there's no save file to initialize it from. Hence, the attempt to create that save file from the non-existing dictionary in addJokeToFavorite: doesn't do anything, either. You need to create an empty dictionary when there is no save file to begin with.
I was just typing this up when Ulrich posted the correct answer. I'll add the rest here for extra clarification.
As Ulrich pointed out, when you don't have a file, your code just skips the initialization of favoriteJokesDictionary and favoriteJokes. When you try to write out the object later, favoriteJokesDictionary is nil and so the method doesn't do anything.
You can just create an empty NSMutableDictionary if the file doesn't exist yet, and since you're retaining part of the dictionary in a separate ivar as well you should create that at the same time. Something like this would work:
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths objectAtIndex:0];
self.favSaveFilePath = [[NSString alloc] initWithString:[documentsDirectory stringByAppendingPathComponent:#"Favorites.plist"]];
if([fm fileExistsAtPath:favSaveFilePath])
{
favoriteJokesDictionary = [[NSMutableDictionary alloc] initWithContentsOfFile:self.favSaveFilePath];
favoriteJokes = [[NSMutableArray alloc] initWithArray:[self.favoriteJokesDictionary objectForKey:#"FavoriteJokes"]];
} else {
favoriteJokesDictionary = [[NSMutableDictionary alloc] init];
favoriteJokes = [[NSMutableArray alloc] init];
[favoriteJokesDictionary setObject:favoriteJokes forKey:#"JokesArrayKey"];
}
That said, I think you could probably simplify your data model there a bit (unless there much more going on that you're not showing). If you need a dictionary because you're storing more than just jokes, then what you have is fine. However, I wouldn't retain the jokes array, because if you later set a new object in the array for your JokesArrayKey, your favoriteJokes ivar is still going to be pointing to the old array.
I would just grab the object from the dictionary instead whenever you need it:
NSMutableArray *jokes = [favoriteJokesDictionary objectForKey:#"JokesArrayKey"];
Even better, if you are working with the jokes array quite a bit, just pull it out into its own file. You can write an NSArray out as a plist just like you can with an NSDictionary. If you're only using the NSDictionary as a shell to write out a .plist, you can skip it entirely.
One other thing: Assuming your favSaveFilePath property is marked "retain", you have a small memory leak in the first section. You're creating a new retained string with [[NSString alloc] initWithString:...], and then retaining it again by assigning it to your property. You probably just want:
self.favSaveFilePath = [documentsDirectory stringByAppendingPathComponent:#"Favorites.plist"];
Referring to the answer aroth gave, non-ns objects in your dictionary may be more subtle than you realise.
EG: I had an NSArray of NSDictionary objects that I was turning into NSObject subclassed items, and adding these to a NSMutableDictionary.
Even though the subclass only contained NS based objects, strings etc; the NSMutableDictionary itself wouldn't save.
The solution was to save the NSArray of NSDictionary items and turn them into my custom subclass after loading the file.