Should I refer to self.property in the init method with ARC?

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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

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