Well Golly

Ternary operators are a concise way to write conditional statements that have two possible outcomes. Rather than writing a longer series of if/then/else statements you can write one line that makes it clear what the two choices are.

In this example from iOS, I use a string for direction—either clockwise or counterclockwise—and translate it to a number for use in the formula. That way I don’t have to remember whether -1 is clockwise or counterclockwise when calling the method. I can use natural language to call the method and let the ternary operator take care of the conversion to the value I need in my formula. And I can change my formula at a later date without having to go back and find all the method calls.

Here’s the method call and the operator

- (void)spin:(NSString *)direction withDuration:(float)duration withScale:(float)scale {
    
    int rotation = ([direction isEqualToString:@"clockWise"] ? 1 : -1);

And then use rotation later to determine which way the object rotates

view.transform = CGAffineTransformRotate(CGAffineTransformScale(transform, 1.0, 1.0), rotation * 2*M_PI/3);

Here’s another example, where I want to pass in a value, but make sure that it isn’t less than one. In this case I’m passing in an integer and rather than doing a series of complicated if/then/else statements I just put the ternary operator in where the integer goes.

self.showRewards = [[ShowRewards alloc] initWithParentView:self.view withLevel:(rewardLevel > 0 ? rewardLevel : 1) ];

I also use it in PHP code for plurals. Something like this is what I use.

$text = "The update was successful. $recordsUpdated " . ($recordsUpdated > 1 ? 'records were updated.' : 'record was updated.');
echo $text;

And I use it to write one set of code that works for two inputs. In this case I have a page that displays all of the titles that are downloadable from Gumroad. Since people are only interested in the Mac or Windows version, I put them on two different pages—but I use the same code. The first part reads in the page type from the URL and puts up a title for Macintosh or Windows.

if ( isset($_GET['page']) ) { $MacWin  = mysql_real_escape_string($_GET['page']); }  else { $MacWin  = 'Win';} 

echo "<div id='wideMargins'>";
$MacintoshWindows = ($MacWin == 'Mac' ? 'Macintosh' : 'Windows');
echo "<h2 class='NewSection'>Download $MacintoshWindows Compatible Titles from Gumroad</h2>";

Then in the SQL statements I pull the appropriate titles. My column names are GumroadURL_Mac and GumroadURL_Win so the $MacWin variable is substituted into the SELECT statement.

$qry = "SELECT *
        FROM product, product_instance
        WHERE product.id = product_id
        AND GumroadURL_$MacWin IS NOT NULL
        ORDER BY name";

I use a full ternary operator to get the right column from the row.

for ($i = 0; $i < $numRows; $i++) {
    $row   = $res->fetch_array();
    $name = $row['name'];
    $tagline = $row['tagline'];
    $GumroadURL = ($MacWin == 'Mac' ? $row['GumroadURL_Mac'] :$row['GumroadURL_Win']);

As you can see, it makes the code much easier to read and in this example, I have one page of code that easily generates two web pages.

This is another programming tool that I don’t recall ever using before. Normally in a loop I cycle through the elements and do something with each item. For example, this Objective C method loops through all the words in the shuffledWords array and returns a list of the words. The for loop in this case uses ‘fast enumeration’ to select each object in the array.

- (Word *)getAndOrButWord:(NSString *)group {
    Word *wordToReturn;
    for( Word *aWord in self.shuffledWords ) {
        if ( [group isEqual:aWord.group] ) {
            wordToReturn = aWord;
        }
    }
    return wordToReturn;
    
}

And this is part of a method that uses the more traditional for loop that explicitly loops through all of the items in an array.

for (NSInteger i = 0; i < [self.prefsCategory1 count]; i++) {
            if ( [[self.prefsCategory1 objectAtIndex:i] isEqualToString: @"1"]) {
                NSString *levelAndPart = [NSString stringWithFormat:@"PREFS01_NAME Part %i", i];
                [self.selectedCategories addObject:levelAndPart];
            }
        }

In both of these cases each item is looked at and appropriate action taken. However, you can break out of the loop early if you don’t need to look at each item. In this simplified example, I only need four items that match the criterion so there is no point in looping after I’ve found four.

for ( Word *gWord in wordsInGroup ) {
    [wordListToReturn addObject:gWord];
    if ( [wordListToReturn count] == 4 ) break;
}
NSLog(@"I've broken out of the loop");

Control goes out of the loop entirely, just as if all the items had been looked at.
Here is a real world example with multiple break statements. In this case I have an array of 200 objects (girls with colored backpacks) and I want four items from the array. The backpacks are colored and have a different colored stripe on them. In the game I ask the child to show me the backpack that is, for example, red and green. But I don’t want to display a green and red backpack on the screen since it would be confusing to the child. There are two breaks in this example. First I loop through the ‘wordListToReturn’ array to see if the backpack can be added. If it can’t then there is no point in looking at the rest of the items in the array so I break out. This takes me to the outer loop and I pick the next object in the backpack array. Once I get four items I don’t need to continue, so there is another break that takes me out of the loop entirely.

NSInteger wordsToReturnCount = 1;
    for ( Word *gWord in wordsInGroup ) {
        // Add the first item to the list
        if ( ![wordListToReturn lastObject]) {
            [wordListToReturn addObject:[wordsInGroup objectAtIndex:0]];
            NSLog(@"First Word added %@", [wordListToReturn objectAtIndex:0]);
        // Loop through after the first word in in the list
        } else {
            BOOL addWord = YES; // Assume you'll add the word unless there is a match
            NSLog(@"gword is %@", gWord.image);
            // Look through all the words in the return list and see if this word matches
            for ( Word *lWord in wordListToReturn) {
                NSArray *gWordColors =[NSArray arrayWithObjects:gWord.color1,   gWord.color2, nil];
                NSArray *lWordColors = [NSArray arrayWithObjects:lWord.color1, lWord.color2, nil];
                
                [gWordColors sortedArrayUsingSelector: @selector(caseInsensitiveCompare:)];
                [lWordColors sortedArrayUsingSelector: @selector(caseInsensitiveCompare:)];
                
                NSString *sortedgWordColors = [NSString stringWithFormat:@"%@ %@", [gWordColors objectAtIndex:0], [gWordColors objectAtIndex:1] ];
                NSString *sortedlWordColors = [NSString stringWithFormat:@"%@ %@", [lWordColors objectAtIndex:0], [lWordColors objectAtIndex:1] ];
                NSLog(@" gWord: %@, lWord %@", sortedgWordColors, sortedlWordColors);
                if ([sortedgWordColors isEqualToString:sortedlWordColors]) {
                    addWord = NO;
                    break;
                }
            }
            if (addWord) {
                [wordListToReturn addObject:gWord];
                NSLog(@"Word added");
                wordsToReturnCount++;
            }
            if (wordsToReturnCount == 4 ) break;
        }
    }