After treating Adil, his doctor prescribes medicines in a complicated dosage. There are two medicinal tablets, one green and one red. The green medicine is to be taken 3 times in the coming week: Monday, Thursday and Saturday and the red one, 4 times: Monday, Wednesday, Friday and Sunday.
As Adil leaves, the doctor hands him two strips of medicine: 7 green tablets and 7 red ones. Adil is confused. He asks, “7 each? But doesn’t it call for 3 of these and 4 of those with a schedule?”. To which, the doctor replies. “How can I be sure that you won’t forget the complicated schedule? That’s why I have given you 7. Have one of each every day.” Adil is aghast. “But… isn’t that over-dosage?” “No, it’s not. 4 of the green tablets are simply mint candies. 3 of the red ones are strawberry candies. Inside the strips, the real tablets are interspersed with identical looking candies as per your dosage schedule. You don’t have to worry. Just habitually have one tablet of each colour every day. Start from the top of each strip.”
Brilliant! The doctor took a complex decision-making process away from Adil and just let him build a simple habit: one green tablet and one red tablet every day. The real tablets will fight against the illness that Adil approached the doctor with. The candies are there to simply … do nothing! In design pattern parlance, the doctor just used the Null Object pattern. Continue reading “Design patterns: Null object”