How to assign words to specific alphabets?

Question

I'm currently making an app similar to Morse Code, to encode, say A = hello, B = good by using isEqualToString method.

-(NSString*)checkWords :(NSString*)words{
NSString * letter;

if (([words isEqualToString:@"a"]) || ([words isEqualToString:@"A"])){
    letter = @"hello";        }
if (([words isEqualToString:@"b"]) || ([words isEqualToString:@"B"])){
    letter = @"good";        }
return letter;

}

By clicking the button below will generate the code:

- (IBAction)decodeBtn:(id)sender {

outputTextField.text = @"";
NSString * inputString = outputView.text;
int wordLength = [inputString length]; //gets a count of length

int i = 0;
while (i < wordLength) {

    unichar charToCheck = [inputString characterAtIndex:i];
    if (charToCheck != 32){ // checks to make sure its not a space

        NSString* words = [NSString stringWithCharacters:&charToCheck length:1];

        NSString * letter = [self checkWords:words];

        NSString * stringToAppend = outputTextField.text;
        if (letter != @""){
            outputTextField.text = [stringToAppend stringByAppendingString:letter];
        } else {
            // new line?
        }
        letter = nil;
    }
    i++;
  }
}

I can get the alphabets to those words I needed. I wonder which method I should use to decode the words back to the alphabets? That is, when user input "hello good" and the output would be "A B"?

Thanks a lot.

If I write in this way, the app crashes:

[EncodeViewController copyWithZone:]: unrecognized selector sent to instance

-(NSString*)checkWords :(NSString*)words{
NSString * letter;

if ([words isEqualToString:@"hello"]) letter = @"A";
if ([words isEqualToString:@"good"]) letter = @"B";

return letter;
}

Answer 1

NSArray* words = [sentence componentsSeparatedByString:@" '];
NSMutableString* output = [NSMutableString string];
for (NSString* word in words) {
   word = [word lowercaseString];
   NSString* letter = [translationDict objectForKey:word];
   [output appendFormat:@"%@ ", letter];
}

To create your translationDict use:

NSDictionary* translationDict = [NSDictionary dictionaryWithObjectsAndKeys:@"apple", @"A", @"banana", @"B", @"chocho", @"C", @"dingodog", @"D", .... @"Z", nil];

You can then use the translation loop either direction (if your individual letters are separated by blanks), with the order of the keys and values reveresed in translationDict.