Objective-C Bool Literals and Macros

Question

Disclaimer: limited knowledge of Objective-C (passing curiosity). ``` if (@YES) ``` vs ``` if (YES) ``` What's the difference? From what I understand, @YES is a bool object literal, and YES is a macro that expands to 1? Is this correct? If so, why use @YES instead of YES or vice versa?

Accepted Answer

`@YES` is a shortcut for `[NSNumber numberWithBool:YES]`, so this:

```
if (@YES)
```

actually means

```
if ([NSNumber numberWithBool:YES] != nil)
```

Note, that it doesn't matter what number (or bool value) that is. You just test that it's a valid object. Even `@NO` will evaulate to `YES` if you test it like that, because it's a non-nil `NSNumber` instance:

```
if (@NO) NSLog(@"test");
```

Output:

```
2013-12-07 21:02:49.828 MyApp[37512:70b] test
```

Long story short: Don't use `@YES` or `@NO` like that, they will not behave as you would expect.

Objective-C Bool Literals and Macros

Solution

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