Question

Well, I know it may sounds basic, but I have literally been looking everywhere and could not find a straight answer to that. I am trying to save location coordinates to a file every time I get an update – sounds simple…. I have two problems: one is with the data type (writeToFile seems to save only NSData) and the other one is with appending to the end of the file. I tried to use NSKeyedArchiver but it wrote a bunch of garbage and I could not find how to append to the end of file with it.

Here is my code – if you could help I would greatly appreciate that. Thanks!

....

NSMutableArray *array = [[NSMutableArray alloc] init];
NSNumber *numLat = [NSNumber numberWithFloat:location.coordinate.latitude];
NSNumber *numLong = [NSNumber numberWithFloat:location.coordinate.longitude];


[array addObject:numLat];    
[array addObject:numLong];    

NSFileHandle *file;
file = [NSFileHandle fileHandleForUpdatingAtPath: @"./location.txt"];

if (file == nil)
    NSLog(@"Failed to open file");


[file seekToEndOfFile];

[file writeData: array]; //BTW - this line doesn't work if I replace array with numLat which is an NSNumber - unlike what many people have said in various discussions here

OR – for the saving to file portion (last two lines):

NSString *path = @"./location.txt";
[NSKeyedArchiver archiveRootObject:array toFile:path];

Answer 1

// Get the path to the Documents (this is where your app saves data)
NSArray *searchPaths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsPath = [searchPaths objectAtIndex: 0];
[array writeToFile:[documentsPath stringByAppendingPathComponent:@"location"] atomically:YES];

To load the data back into the array, use

NSArray *searchPaths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsPath = [searchPaths objectAtIndex: 0];
array = [[NSMutableArray alloc] initWithContentsOfFile:[documentsPath stringByAppendingPathComponent:@"location"];