如何将NSArray保存到文件并从文件中检索NSArray

Question

I have been trying to implement the answers given at is it possible to save NSMutableArray or NSDictionary data as file in iOS? and they have not been working for me. Will someone please inform me of what I am doing wrong? My NSArray is of a custom object, say Cat . Cat itself is constituted of strings and numbers. Here is my code

-(void)saveArrayToFile:(NSArray *)response;
{
//    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
//    NSString *documentsDirectory = [paths objectAtIndex:0];
//    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:PERSISTENT_FILENAME];
//    
//    [response writeToFile:filePath atomically:YES];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
    if ([paths count] > 0)
    {
        // Path to save array data
        NSString  *arrayPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"array.out"];
        // Write array
        [response writeToFile:arrayPath atomically:YES];


    }else NSLog(@"NO paths");
}

-(NSArray *)getArrayFromFile
{
//    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
//    NSString *documentsDirectory = [paths objectAtIndex:0];
//    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:PERSISTENT_FILENAME];
//    return [NSArray arrayWithContentsOfFile:filePath];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
    if ([paths count] > 0)
    {
        // Path to save array data
        NSString  *arrayPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"array.out"];
        NSArray *arrayFromFile = [NSArray arrayWithContentsOfFile:arrayPath];
        return arrayFromFile;
    }else NSLog(@"No file to retrieve");
    return nil;
}

First I tried the commented code. Then I tried the other. The problem so far is that the file is not being saved.

Answer 1

When you save it [response writeToFile:arrayPath atomically:YES] return false. So it is not saved successfully. Try use

Bool result = [NSKeyedArchiver archiveRootObject:response toFile:arrayPath];
NSArray *arrayFromFile = [NSKeyedUnarchiver unarchiveObjectWithFile:arrayPath];

In your cat file:

@property(nonatomic, strong)NSString* score;
@property(nonatomic, assign)BOOL bGenuine;
@property(nonatomic, assign)NSInteger errorCode;

@synthesize score,bGenuine,errorCode;

- (void)encodeWithCoder:(NSCoder *)encoder {
    [encoder encodeObject:score forKey:@"score"];
    [encoder encodeObject:[NSNumber numberWithBool:bGenuine] forKey:@"bGenuine"];
    [encoder encodeObject:[NSNumber numberWithInt:errorCode] forKey:@"errorCode"];
}

- (id)initWithCoder:(NSCoder *)decoder {
    score = [decoder decodeObjectForKey:@"score"];
    bGenuine = [[decoder decodeObjectForKey:@"bGenuine"] boolValue];
    errorCode = [[decoder decodeObjectForKey:@"errorCode"] integerValue];
    return self;
}

Answer 2

If the array's contents are all property list objects (NSString, NSData, NSArray, or NSDictionary objects), the file written by this method can be used to initialize a new array with the class method arrayWithContentsOfFile: or the instance method initWithContentsOfFile:.

This might be the reason why you can't read the file if your array contains custom objects

Alternatively try to use NSKeyedArchiver