| 摘要 |
A conversion path for converting between two different currencies is defined as a series of simple exchange rate objects and is encapsulated within a compound exchange rate object. The intelligence regarding the specific rules for making the conversion are encapsulated in a policy class, which governs how the path of exchange rates contained in the compound exchange rate is built. When a client requests conversion between two currencies, the compound exchange rate is constructed according to the policy to contain a path of exchange rate objects that may be used to make the requested conversion, and the compound exchange rate is then returned to the client. When the client then instructs the compound exchange rate to make a conversion of a known currency value in the source currency, the compound exchange rate object uses the exchange rate object or objects in the exchange rate path to perform the currency conversion. A system in accordance with the invention thus allows the computation of exchange rates in a fully encapsulated manner according to a predefined policy without the client having to know the details of how the conversion is performed.
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