If this was coded as follows, then there would be no need to strongify:
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NSString *quantityLabelString = [newValue stringValue];
if([self.quantitySuffix length])
    quantityLabelString = [NSString stringWithFormat: @"%@ %@", [newValue stringValue], self.quantitySuffix];

viewDelegate.quantityLabel.text = quantityLabelString;
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