Objective-C 101 (retain vs assign) NSString
ios, iphone, nsstring, objective-c, retain
Solution
There's no such thing as the "scope of an object" in Objective-C. Scope rules have nothing to do with an object's lifetime — the retain count is everything.
You usually need to claim ownership of your instance variables. See the Objective-C memory management rules. With a `retain` property, your property setter claims ownership of the new value and relinquishes ownership of the old one. With an `assign` property, the surrounding code has to do this, which is just as mess in terms of responsibilities and separation of concerns. The reason you would use an `assign` property is in a case where you can't retain the value (such as non-object types like BOOL or NSRect) or when retaining it would cause unwanted side effects.
Incidentally, in the case of an NSString, the correct kind of property is usually `copy`. That way it can't change out from under you if somebody passes in an NSMutableString (which is valid — it is a kind of NSString).
Problem
A 101 question Let's say i'm making database of cars and each car object is defined as: ``` #import <UIKit/UIKit.h> @interface Car:NSObject{ NSString *name; } @property(nonatomic, retain) NSString *name; ``` Why is it `@property(nonatomic, retain) NSString *name;` and not `@property(nonatomic, assign) NSString *name;`? I understand that `assign` will not increment the reference counter as `retain` will do. But why use `retain`, since `name` is a member of the `todo` object the scope of it is to itself. No other external function will modify it either.