6.3. Delegation and Callback
Component-based design is “divide and conquer” with clear-cut compartmentalization: Sharing among bundles and services is strictly controlled. This poses a challenge to designing services that work together. For multiple callers to use a service, they must go through the same interface provided by the callee; at the same time, they may all want the callee in slightly different ways.
Suppose we are to design a news service, NewsService, whose HTML contents are needed by services for a pager, a touch panel, and a PC. The data are from the same source, but how they are displayed varies: text only on the pager, no dynamic contents on the touch panel, and full media on the PC.
The news service has a few options to deal ...
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