Help with NSString of int's to NSString of ASCII characters? - iphone

Question

I have implemented some code to convert a NSString of "text" to an NSString of (ASCII) ints, like so:
#"Hello" is converted to #"72 101 108 108 111"
However, I am having quite a bit of difficulty doing the opposite. Starting with a string of ints (with the spaces) and converting back to the plain string of text.
What I need: #"72 101 108 108 111" must be converted to #"Hello"
I have tried breaking up the input string into an int array, iterating through it, and using repeatedly the following:
[NSString stringWithFormat:#"%c", decCharArray[i]]
However, the problem with that is that it parses each particular digit into ASCII, converting the 7, the 2, the space, the 1, etc.
Thanks a ton in advance.

Answer 1

Sounds like you have the right approach. Try using [string componentsSeparatedByString:#" "] to split the string at the spaces. Then you can convert each of those to numbers, and back into strings.

Answer 2

There is no real magic on it. Since you'll be using ASCII, to convert an int
to a char all you have to do is an assignment, as you may already know:
char a = 65; /* a contains 'A' */
NSString has a very convenient method componentsSeparatedByString: that will
return an array of strings containing your numbers, and you can get an int
from a string with the intValue method. Thus, all you have to do is to split
the string and iterate through the components assigning their int value to a
char array. Here is an example function that does that:
NSString *
TextFromAsciiCodesString (NSString *string)
{
NSArray *components = [string componentsSeparatedByString:#" "];
NSUInteger len = [components count];
char new_str[len+1];
int i;
for (i = 0; i < len; ++i)
new_str[i] = [[components objectAtIndex:i] intValue];
new_str[i] = '\0';
return [NSString stringWithCString:new_str
encoding:NSASCIIStringEncoding];
}
And a simple use of it, with your "Hello" example:
NSString *string = #"72 101 108 108 111";
NSLog(#"%#", TextFromAsciiCodesString(string));
Actually, it's a bit different as your example was "Hell^K" :-)

Answer 3

You can also trying using NSString's enumerateSubstringsInRange:options:usingBlock:.
Usage
NSString * hello = #"72 101 108 108 111";
NSMutableString * result = [NSMutableString string];
[hello enumerateSubstringsInRange:NSMakeRange(0, [data length])
options:NSStringEnumerationByWords
usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[result appendString:[NSString stringWithFormat:#"%c", [substring intValue]]];
}];
NSLog(#"%#", result);