Swap Pricing Strategies at Runtime

Hard ⏱ 18 min 32% acceptance ★★★★☆ 4.2

Implement the strategy pattern: classes FlatRate(fee) and PerKg(rate) each expose cost(weight). Shipment(weight, strategy) delegates price() to whichever strategy object it holds, and set_strategy() swaps it live. The shipment never contains pricing math itself.

Examples

Example 1

Input

s = Shipment(3, PerKg(40)); s.price(); s.set_strategy(FlatRate(99)); s.price()

Output

120 then 99

Explanation

Same shipment, different interchangeable pricing objects.

Constraints

Both strategies share the cost(weight) interface.
Shipment.price only delegates.

Topics

OOPstrategy pattern

Companies

AmazonFedExDelhivery

Hints

Hint 1

Duck typing is the whole pattern here — no base class required.

Hint 2

Store the strategy as an attribute.

← Immutable Coordinates Duck-Typed Notification Fan-out →

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