How can I split up GPS coordinate in Objective C?

Question

I need to extract the different components from a GPS coordinate string. So for example:

+30° 18' 12" N  // pull out 30, 18 & 12

or

+10° 11' 1" E    // pull out 10, 11 & 1

or

-3° 1' 2" S    // pull out -3, 1 & 2

or

-7° 12' 2" W    // pull out -7, 12 & 2

I have had a look around online and I notice there is the NSRegularExpression. I was wondering if it's possible to use this in some way? I have also had a look at the documentation provided and I have tried to put together a regex to pull out the different parts. This is what I came up with:

('+'|'-')$n°\s$n'\s$n"\s(N|E|S|W)

I'm not really sure if this is correct or not, I'm also unclear on how to use it since there aren't many tutorials/example around. Please could someone help me out? If there is a better way of doing this rather than using NSRegularExpression I'm open to it, however as far as I'm aware objective c does't have any built in regex support.

Answer 1

Using NSScanner:

NSScanner *scanner;
NSCharacterSet *numbersSet = [NSCharacterSet characterSetWithCharactersInString:@" °'"];
int degrees;
int minutes;
int seconds;

NSString *string = @" -7° 12' 2\" W";
scanner = [NSScanner scannerWithString:string];
[scanner setCharactersToBeSkipped:numbersSet];
[scanner scanInt:&degrees];
[scanner scanInt:&minutes];
[scanner scanInt:&seconds];
NSLog(@"degrees: %i, minutes: %i, seconds: %i", degrees, minutes, seconds);

NSLog Output:

degrees: -7, minutes: 12, seconds: 2

Answer 2

RegExps are an overkill, IMHO. Use [NSString componentsSeparatedByString:] with space as the separator to split the string into parts, then [NSString intValue] to tease the numeric value of each component except for the last one.

Answer 3

NSMutableArray *newCoords = [[NSMutableArray alloc] init];
NSArray *t = [oldCoords componentsSeparatedByString: @" "];

[newCoords addObject: [[t objectAtIndex: 0] intValue];
[newCoords addObject: [[t objectAtIndex: 1] intValue];
[newCoords addObject: [[t objectAtIndex: 2] intValue];

Assuming you had the coordinates given in your post in NSString oldCoords, this would result in an NSMutableArray called newCoords which would contain the three pieces of data you need.

Answer 4

RE's overkill (Seva)? How about objects? ;-)

NSString *coords = @"+30° 18' 12\" N";

int deg, sec, min;
char dir;

if(sscanf([coords UTF8String], "%d° %d' %d\" %c", &deg, &min, &sec, &dir) != 4)
   NSLog(@"Bad format: %@\n", coords);
else
   NSLog(@"Parsed %d deg, %d min, %d sec, dir %c\n", deg, min, sec, dir);

Whether you like this depends on your view of dropping into C, but it is direct and simple.

Answer 5

The re you need is: @"([+-]?[0-9]+)"

Here is example code:

NSString *string;
NSString *pattern;
NSRegularExpression *regex;
NSArray *matches;

pattern = @"([+-]?[0-9]+)";

regex = [NSRegularExpression
         regularExpressionWithPattern:pattern
         options:NSRegularExpressionCaseInsensitive
         error:nil];

string = @" -7° 12' 2\" W";
NSLog(@"%@", string);
matches = [regex matchesInString:string options:0 range:NSMakeRange(0, [string length])];
degrees = [[string substringWithRange:[[matches objectAtIndex:0] range]] intValue];
minutes = [[string substringWithRange:[[matches objectAtIndex:1] range]] intValue];
seconds = [[string substringWithRange:[[matches objectAtIndex:2] range]] intValue];
NSLog(@"degrees: %i, minutes: %i, seconds: %i", degrees, minutes, seconds);

NSLog output:

degrees: -7, minutes: 12, seconds: 2