Simple stringByReplacingOccurrencesOfString help issue - ios

Question

I want to replace some "ilegal" characters from a string to another "legal" characters, I have this code:
- (NSString *) quitarTildes:(NSString *)aStr
{
NSString *aux = aStr;
NSString *invalid = #"áéíóúÁÉÍÓÚñÑ";
NSString *valid = #"aeiouAEIOUnN";
for (int i = 0; i < [invalid length]; i++)
[aux stringByReplacingOccurrencesOfString: [NSString stringWithFormat:#"%c",[invalid characterAtIndex:i]]
withString: [NSString stringWithFormat:#"%c",[valid characterAtIndex:i]]];
NSLog(#"%#",aux);
return aux;
}
And all ilegal character still there...
NSString *test = #"Hólá, Ésto es una prueba.";
test = [self quitarTildes: test];
NSLog, response:
2013-04-04 08:58:52.896 GeoRuta_v1[1960:907] Hólá, Ésto es una prueba.

Answer 1

From the documentation:
stringByReplacingOccurrencesOfString:withString: Returns a new string
in which all occurrences of a target string in the receiver are
replaced by another given string.
-(NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement
So:
aux = [aux stringByReplacingOccurrencesOfString: [NSString stringWithFormat:#"%c",[invalid characterAtIndex:i]]
withString: [NSString stringWithFormat:#"%c",[valid characterAtIndex:i]]];

Answer 2

A perhaps simpler solution to achieve your goal:
NSString *test = #"Hólá, Ésto es una prueba. - áéíóúÁÉÍÓÚñÑ";
test = [test stringByFoldingWithOptions:NSDiacriticInsensitiveSearch locale:NULL];
NSLog(#"%#", test);
Output:
Hola, Esto es una prueba. - aeiouAEIOUnN

Answer 3

One. You're using the wrong format specifier for characterAtIndex:. That method returns unichar and not char (for obvious reasons). You have to use %C (capital C).
Two. You're returning the original string, and not replacing its characters.
NSMutableString *tmp = [aStr mutableCopy];
// ...
[tmp replaceOccurrencesOfString:[NSString stringWithFormat:#"%C", [invalid characterAtIndex:i]]
withString:[NSString stringWithFormat:#"%C", [valid characterAtIndex:i]]];