Why underscore synthesize

No, they're not. Those are references to the properties window and viewController. That's the point of the underscore, to make it clearer when the property is being used no underscore and when the ivar is being accessed directly with underscore. Yes, Its is just to differentiate the reference of object. That is , if the object is referred directly use it with underscore, otherwise use self to refer the object. Why rename synthesized properties in iOS with leading underscores? Another point of confusion; in the app delegate implementation, after synthesizing the window iVar as above, in the application didFinishLaunchingWithOptions: method the window and viewController ivars are referred to using self: self.

Asked By: Alpinista. Thank you in advance. I have searched many questions on ObjC accessors and synthesized accessors to no avail. This question is more of a "help me settle an issue" question; I don Any takers? I am trying to access elements of a dict with keys that start with the underscore character. I have a piece of C code that calls a function defined in assembly.

By way of example, let's say foo. Any other ideas? Login using GitHub. Related questions objective c - Are synthesized instance variables generated as private instead of protected? Powered by Question2Answer. How exactly getter and setter methods body looks like after they have been automatically synthesized? From official documentation I found so far only recommended I recently tried to compile an older Xcode project which used to compile just fine , and now I'm seeing a lot of errors of this form: error: writable Is that the only way?

Since recent runtimes in iOS, we are able to define properties that will generate accessors for instance variables. It will also generate the accessor methods with the proper semantics to match the property declaration. If you explicitly synthesize a property with the synthesize keyword, then the compiler will do something similar but slightly different. If your synthesize statement doesn't explicitly associate an instance variable name with the property, then it will use a variable name without a leading underscore.

To use the conventional name, you'd need to be explicit:. The second difference is that explicit synthesis can be combine with manual implementation. The compiler will provide the pieces instance variable, getter, setter that you do not.

Now, to the code you showed. You have declared a property "title". You have implemented a method -setTitleForBook:. Technically, these two have nothing to do with one another. Because you didn't override the default setter in the property declaration, that tells both users of your class and the compiler that the setter has the conventional name, -setTitle:.

Then, when the compiler synthesizes the property, it's generating an implementation of -setTitle:, too. That's probably going to get you in trouble down the line, because some user of this class is going to write. The same thing goes for -setAuthorForBook:. You could address this in two ways. One solution would be to inform users of your class and the compiler about this by changing the property declaration to:.

Another solution would be to use the conventional name. My recommendation is to use the conventional name.