A quick question.
if I have a property and an ivar declared with the same name:
in the .h file:
(Reminder*)reminder;
@property(nonatomic,strong)(Reminder*)reminder;
in the .m file, should I use the ivar or the property in the init method if I'm using ARC?
- (id)initWithReminder:(Reminder*)reminder_ {
self = [super init];
if (self) {
reminder = reminder_;
}
return self;
}
Or should I use the property to get the benefit of the automatic reference counting like this:
- (id)initWithReminder:(Reminder*)reminder_ {
self = [super init];
if (self) {
self.reminder = reminder_;
}
return self;
}
I'm not sure at which point in the object's initialization the properties become accessible with the dot notation.
Use direct access in partially constructed states, regardless of ARC:
- (id)initWithReminder:(Reminder*)reminder_ {
self = [super init];
if (self) {
reminder = reminder_;
// OR
reminder = [reminder_ retain];
}
return self;
}
This is because self.whatever
will trigger other side effects, such as Key-Value Observing (KVO) notifications, or maybe your class implements (explicitly) or a subclass overrides setWhatever:
-- and that could expose your partially initialized instance to other APIs (including its own), which rightly assume they are dealing with a fully constructed object.
You could manually verify that a class is capable of operating in a partially initialized state, but that requires a lot maintenance and is (frankly) impractical or impossible when other people want to subclass your class. It requires a lot of time and maintenance, and there isn't substantiative benefit doing so, especially if you try to use the approach as a convention.
So the uniform manner which guarantees correctness is to use direct access in partially constructed states, and avoid using the accessors.
Note: I am using "partially constructed" because initialization is only half of the picture; -dealloc
has similar caveats.
Some more detail as to why you should use direct access in partially constructed states (ARC || MRC) can be found here: Initializing a property, dot notation