I have a form with information first name and last name and some other information. I use a person class to store this information. on submit click I archiving it in a file person.txt using NSCoding implemented in person class. if I add multiple persons in the file person.txt, how can I get all the person objects stored in the file. decoding the person class just gives me the last added person.
If you want all of the person objects serialized, then you need the NSArray or whatever other collection class in which they are stored to be the root object for the NSKeyedArchiver. e.g.: (assumes ARC)
#import <Foundation/Foundation.h>
#interface Person:NSObject <NSCoding>
#property (nonatomic, copy) NSString *lastName;
#property (nonatomic, copy) NSString *firstName;
// etc.
#end
#implementation Person
#synthesize lastName = _lastName;
#synthesize firstName = _firstName;
- (void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:self.lastName forKey:#"ln"];
[aCoder encodeObject:self.firstName forKey:#"fn"];
}
- (id)initWithCoder:(NSCoder *)aDecoder {
self = [super init];
if( !self ) { return nil; }
_lastName = [aDecoder decodeObjectForKey:#"ln"];
_firstName = [aDecoder decodeObjectForKey:#"fn"];
return self;
}
#end
int main(int argc, char *argv[]) {
NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];
Person *me = [Person new];
me.lastName = #"Kitten";
me.firstName = #"Mittens";
Person *you = [Person new];
you.lastName = #"Youe";
you.firstName = #"JoJo";
NSArray *people = [NSArray arrayWithObjects:me,you,nil];
NSData *serializedData = [NSKeyedArchiver archivedDataWithRootObject:people];
// write your serializedData to file, etc.
[p release];
}
Why the .txt extension on your archive, though? It just binary data, right?
Related
I trying to learn how to save array of objects using NSKeyedArchiver and I coded a small application to do that and I logged to see if the array was saved but everytime I get 0 for array count and here is the code.
ViewController.h
#interface ViewController : UIViewController
{
IBOutlet UITextField *text;
IBOutlet UITextField *textName;
IBOutlet UITextField *textAge;
IBOutlet UILabel *name;
IBOutlet UILabel *age;
BOOL flag;
BOOL choice;
NSString *documentDirectory;
NSMutableArray *anArray;
Person *p;
NSData *data;
}
-(BOOL) dataFilePath;
-(IBAction)readPlist;
-(IBAction) writePlist;
#property (strong,nonatomic)IBOutlet UITextField *text;
#property (strong,nonatomic)IBOutlet UITextField *textName;
#property (strong,nonatomic)IBOutlet UITextField *textAge;
#property (strong,nonatomic)IBOutlet UILabel *name;
#property (strong,nonatomic)IBOutlet UILabel *age;
#property (strong,nonatomic)NSString *documentDirectory;
#property (strong,nonatomic)NSMutableArray *anArray;
#end
ViewController.m
#interface ViewController ()
#end
#implementation ViewController
#synthesize text,documentDirectory,textAge,textName,name,age,anArray;
- (void)viewDidLoad
{
[super viewDidLoad];
// checking if the file was created and show a message if its created or not.
if ([self dataFilePath]) {
NSLog(#"File Created !");
} else {
NSLog(#"File Not Created !");
}
NSLog(#"File location : %#",documentDirectory);
choice = YES;
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(BOOL) dataFilePath
{
NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentDirectory = [path objectAtIndex:0];
documentDirectory = [documentDirectory stringByAppendingPathComponent:#"MilmersÂData.dat"];
return TRUE;
}
- (IBAction)writePlist
{
p.name = textName.text;
p.age = [textAge.text intValue];
[anArray addObject:p];
for (int i=0; i<[anArray count]+1; i++) {
Person *pp = [[Person alloc]init];
pp=[anArray objectAtIndex:i];
NSLog(#"Name: %#",pp.name); // checking the names in pp object but getting null
}
data = [NSKeyedArchiver archivedDataWithRootObject:anArray];
[data writeToFile:documentDirectory options:NSDataWritingAtomic error:nil];
NSLog(#"Array length: %d",[anArray count]); //Always got array count zero.
}
-(IBAction)readPlist
{
NSString *filePath = documentDirectory;
NSMutableArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
NSLog(#"The array is: %#",array); // it shows that there is nothing in the array
}
#end
I wrote the class for writing .plist files originally but I knew later that I cant store objects in .plist file so I tried so that with archive, thats why the method name have plist in it.
Thank you in advance
Looks like you aren't ever creating an instance of p to add to the array. Try:
Person *p = [[Person alloc] init];
p.name = textName.text;
p.age = [textAge.text intValue];
[anArray addObject:p];
your index limit was also wrong in this loop
for (int i=0; i<[anArray count]; i++) {
NSLog(#"Name: %#", [[anArray objectAtIndex:i] name]);
}
you should really have been seeing a couple of different crashes...
Try adding this in viewDidLoad
[[NSFileManager defaultManager] createFileAtPath:documentDirectory contents:nil error:nil];
It looks like you never do this, and using archives to write to files only works if the file already exists (make sure you only do this once, otherwise every time that view is loaded the file will be emptied of all the data in it). And when you do this
if ([self dataFilePath])
It's pointless, because no matter what it always returns yes, whether the file exists or not.
Does your Person class implement NSCoding?
Specifically you need to implement something like the following in Person.m:
- (id)initWithCoder:(NSCoder *)decoder {
self = [super init];
if (!self) {
return nil;
}
self.name = [decoder decodeObjectForKey:#"name"];
self.age = [decoder decodeObjectForKey:#"age"];
return self;
}
- (void)encodeWithCoder:(NSCoder *)encoder {
[encoder encodeObject:self.name forKey:#"name"];
[encoder encodeObject:self.age forKey:#"age"];
}
So in my model I have the following code... I am successfully able to return each individual value. I want to know how am I able to return the entire speakerTable []... Maybe some advice. Thanks!
typedef struct {
NSUInteger speakerID;
NSString * speakerName;
NSString * speakerPosition;
NSString * speakerCompany;
} SpeakerEntry;
static const SpeakerEntry speakerTable [] =
{
{0, #"name", #"position", #"company"},
{1, #"name", #"position", #"company"},
{-1, nil, nil, nil}
};
This works correctly...
-(NSString *) stringSpeakerCompanyForId:(NSUInteger) identifier{
NSString * returnString = nil;
if ([self helpCount] > identifier) {
returnString = speakerTable[identifier].speakerCompany;
}
return returnString;
}
This does not work at all..
-(id) getSpeaker{
//if ([speakerTable[0].speakerName isKindOfClass:[NSString class]])
// NSLog(#"YES");
NSArray * myArray3 = [NSArray arrayWithArray:speakerTable];
return myArray3;
}
arrayWithArray expects an NSArray, not a C array.
The first one works because you are using it like a C array.
Alternatively - don't use a struct, use an object instead:
Create a class called Speaker.
In Speaker.h
#interface Speaker : NSObject {}
#property (nonatomic, assign) NSUinteger id;
#property (nonatomic, copy) NSString name;
#property (nonatomic, copy) NSString position;
#property (nonatomic, copy) NSString company;
- (void)initWithId:(NSUInteger)anId name:(NSString *)aName position:(NSString *)aPosition company:(NSString *)aCompany;
#end
in Speaker.m
#import "Speaker.h"
#implementation Speaker
#synthesize id, name, position, company;
- (void)initWithId:(NSUInteger)anId name:(NSString *)aName position:(NSString *)aPosition company:(NSString *)aCompany {
if (!([super init])) {
return nil;
}
id = anId;
NSString name = [[NSString alloc] initWithString:aName];
NSString position = [[NSString alloc] initWithString:aPosition];
NSString company = [[NSString alloc] initWithString:aCompany];
return self;
}
- (void)dealloc {
[name release];
[position release];
[company release];
[super dealloc];
}
#end
And now in your calling code you can create an immutable array of speakers with:
Speaker *speaker0 = [[Speaker alloc] initWithId:0 name:#"name0" position:#"position0" company:#"company0"];
Speaker *speaker1 = [[Speaker alloc] initWithId:1 name:#"name1" position:#"position1" company:#"company1"];
Speaker *speakerNull = [[Speaker alloc] initWithId:-1 name:nil position:nil company:nil];
NSArray *speakerArray [[NSArray arrayWithObjects: speaker0, speaker1, speakerNull] retain]
[speaker0 release];
[speaker1 release];
[speakerNull release];
note: this is typed straight in, so feel free to mention/correct typos or errors
The method arrayWithArray takes in an NSArray as an argument, not a C array.
I've built a singleton object to manage some data in my app
#interface MyCommon : NSObject {
NSArray *quizz;
int iCurrentQuestion;
};
+ (MyCommon *)singleton;
#property (retain) NSArray *quizz;
#property (assign) int iCurrentQuestion;
#end
MyCommon.m
#import "MyCommon.h"
// MyCommon.m:
#implementation MyCommon
static MyCommon * MyCommon_Singleton = nil;
#synthesize iCurrentQuestion;
+ (MyCommon *)singleton
{
if (nil == MyCommon_Singleton)
{
MyCommon_Singleton = [[MyCommon alloc] init];
NSLog(#"allocating MyCommon_Singleton at %#",MyCommon_Singleton);
}
else {
NSLog(#"accessing singleton : %#", MyCommon_Singleton);
}
return MyCommon_Singleton;
}
- (NSArray*) getQuizz{
return quizz;
}
- (void) setQuizz:(NSArray *)array {
quizz = [NSArray arrayWithArray:array];
NSLog(#"setQuizz : %#",quizz);
}
There is no problem for writing the quizz object (setQuizz), however when I try to access it for reading, I get a crash : the quizz looks invalid and Xcode notify me an invalid CFArrayRef
I don't know what's wrong with my code.
You provide a custom setter for quizz but it doesn't comply with how the property is declared.
You're not retaining quizz when you're setting a new value. It's likely to be released just after, leading to a crash when you access it.
You should write
- (void)setQuizz:(NSArray *)array {
if (quizz != array) {
NSArray *tmp = quizz;
quizz = [array retain]; // retain the new value
[tmp release]; // release the old one
}
NSLog(#"setQuizz : %#",quizz);
}
this is way more code than it needs to be. First if you are going to be providing your own method you should declare so in the #property declaration which you didn't. Also your not properly retaining your variables. Additionally you should be using dispatch_once() for a thread safe & fast way to guarantee the singleton is only created once.
#interface MyCommon : NSObject {}
#property(nonatomic, retain) NSArray *quiz;
#property (assign) int iCurrentQuestion;
+ (MyCommon *)singleton;
#end
#implementation MyCommon
#synthesize quiz;
#synthesize iCurrentQuestion;
-(id)init {
self = [super init];
if(self) {
quiz = [[NSMutableArray alloc init];
iCurrentQuestion = 0;
}
return self;
}
+ (MyCommon *)singleton {
static MyCommon *singleton = nil;
static dispatch_once_t pred;
dispatch_once(&pred, ^{
singleton = [[MyCommon alloc] init];
});
return singleton;
}
#end
then you just do
[MyCommon singleton].quiz = //some array
Can anyone give me clear picture about dynamic property and its usage? y not use the usual #property everywhere?
Dynamic properties are used when you don't provide an implementation at compile time, but ensure that one exists at runtime. Being a dynamic language, Objective-C can respond to messages at runtime, even if the class doesn't have an implementation at compile time.
Here's a contrived example: Let's say you have a Book class, backed by an NSMutableDictionary that contains the keys title and author. However, you want Book to respond to title and author as well, and have them as properties; title and author will grab the appropriate value from the dictionary, and setTitle: and setAuthor: will change the value stored in the dictionary. You could do so with this code:
#import <Foundation/Foundation.h>
#interface Book : NSObject
{
NSMutableDictionary *data;
}
#property (retain) NSString *title;
#property (retain) NSString *author;
#end
#implementation Book
#dynamic title, author;
- (id)init
{
if ((self = [super init])) {
data = [[NSMutableDictionary alloc] init];
[data setObject:#"Tom Sawyer" forKey:#"title"];
[data setObject:#"Mark Twain" forKey:#"author"];
}
return self;
}
- (void)dealloc
{
[data release];
[super dealloc];
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector
{
NSString *sel = NSStringFromSelector(selector);
if ([sel rangeOfString:#"set"].location == 0) {
return [NSMethodSignature signatureWithObjCTypes:"v#:#"];
} else {
return [NSMethodSignature signatureWithObjCTypes:"##:"];
}
}
- (void)forwardInvocation:(NSInvocation *)invocation
{
NSString *key = NSStringFromSelector([invocation selector]);
if ([key rangeOfString:#"set"].location == 0) {
key = [[key substringWithRange:NSMakeRange(3, [key length]-4)] lowercaseString];
NSString *obj;
[invocation getArgument:&obj atIndex:2];
[data setObject:obj forKey:key];
} else {
NSString *obj = [data objectForKey:key];
[invocation setReturnValue:&obj];
}
}
#end
int main(int argc, char **argv)
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
Book *book = [[Book alloc] init];
printf("%s is written by %s\n", [book.title UTF8String], [book.author UTF8String]);
book.title = #"1984";
book.author = #"George Orwell";
printf("%s is written by %s\n", [book.title UTF8String], [book.author UTF8String]);
[book release];
[pool release];
return 0;
}
Note the the methods are "created" at runtime via forwardInvocation:; hence, title and author are dynamic properties.
(This isn't the best example, but I think it gets the point across.)
#dynamic thing; is merely a way to inform the system not to generate getters/setters for the thing, that you (or someone else) will provide them for you—As in, they'll be there at runtime.
This is in contrast to #synthesize which tells the compiler to generate the getter/setter (as appropriate) for you.
#dynamic is (in my experience) used primarily in conjunction with Core Data and subclasses of NSManagedObject. To quote Marcus Zarra's Core Data,
By declaring them
[attributes/relationships], we are
telling the compiler to ignore any
warnings associated with there
properties because we "promise" to
generate them at runtime. Naturally,
if the turn up missing at runtime,
then our application is going to
crash.
For a little iPhone application I am making, I want to sort a NSMutableArray.
I found 2 ways of doing this, but they both result in the same thing. Sorting the array will cause some objects to 'overwrite' eachother.
First off, here is my code:
AppDelegate.h
NSMutableArray* highScores;
Somewhere down that AppDelegate.h, I also make this variable a property so that I can access it from differen classes:
#property (retain, nonatomic) NSMutableArray* highScores;
When my application starts, I read the high scores from a file and import them into my NSMutableArray.
AppDelegate.m
NSMutableData* data = [NSData dataWithContentsOfFile:highScoresPath];
NSKeyedUnarchiver* decoder = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
self.highScores = [decoder decodeObjectForKey:#"highscoresArray"];
The objects I store in this NSMutableArray are from the type HighScore.
HighScore.h
#interface HighScore : NSObject {
int score;
int roundsPlayed;
int wrongAnswers;
NSString* name;
NSDate* datetime;
}
#property int score;
#property int roundsPlayed;
#property int wrongAnswers;
#property (nonatomic, copy) NSDate* datetime;
#property (nonatomic, copy) NSString* name;
- (id) init;
- (void) update:(int)roundScore:(BOOL) correct;
#end
HighScore.m
#import "HighScore.h"
#implementation HighScore
#synthesize score, roundsPlayed, wrongAnswers, name, datetime;
- (id) init
{
self.name = #"";
self.score = 0;
self.roundsPlayed = 0;
self.wrongAnswers = 0;
self.datetime = [NSDate date];
return self;
}
- (void) update:(int)roundScore:(BOOL) correct
{
self.score += roundScore;
if (!correct)
self.wrongAnswers++;
self.roundsPlayed++;
self.datetime = [NSDate date];
}
- (id) initWithCoder:(NSCoder *) decoder
{
self.name = [[decoder decodeObjectForKey:#"name"] retain];
self.score = [decoder decodeIntForKey:#"score"];
self.roundsPlayed = [decoder decodeIntForKey:#"roundsPlayed"];
self.wrongAnswers = [decoder decodeIntForKey:#"wrongAnswers"];
self.datetime = [[decoder decodeObjectForKey:#"datetime"] retain];
return self;
}
- (void) encodeWithCoder:(NSCoder *)encoder
{
[encoder encodeObject:self.name forKey:#"name"];
[encoder encodeInt:self.score forKey:#"score"];
[encoder encodeInt:self.roundsPlayed forKey:#"roundsPlayed"];
[encoder encodeInt:self.wrongAnswers forKey:#"wrongAnswers"];
[encoder encodeObject:self.datetime forKey:#"datetime"];
}
- (NSComparisonResult) compareHighscore:(HighScore*) h
{
return [[NSNumber numberWithInt:self.score] compare:[NSNumber numberWithInt:h.score]];
}
#end
Now, when I try to sort my array by using the following code:
NSArray *sortedArray;
sortedArray = [highScores sortedArrayUsingSelector:#selector(compareHighscore:)];
It somehow screws up my highScores array, I get an X amound of highscores with the same score and name.
What am I doing wrong?
I'm noticing that in your initWithCoder: method, you're not doing this:
if (self = [super initWithCoder:coder]) {
// Decode your stuff here
}
Same with your regular init method. There needs to be a call to [super init].
Also, since you defined your string properties as copy and you're using the property syntax, there's no need to retain them. They will be retained for you by the synthesized accessor.
Otherwise, your code looks fine to me. Just remember: every init method must always have a call to a super's init... method.
You're trying to sort using #selector(compare:), not #selector(compareHighscore:), which I presume was your intention.
try
sortedArray = [highScores sortedArrayUsingSelector:#selector( compareHighscore: )];
Post the actual compareHighscore: method. The most important thing is that it has to be consistent, that is if a <= b and b <= c, then a <= c and if a < b and b < c then a < c. If you managed to write a compare method that is not consistent, anything can happen.