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| <body> |
| <h1>Step 2 - Zest™ "Making a booking."</h1> |
| |
| <p> |
| Location: Page 17, "Knowledge-Rich Design. |
| </p> |
| |
| <h2>Results from Step1</h2> |
| <ul> |
| <li>For the Cargo and Voyage interfaces, we have introduced the <i>Property<Double></i>. |
| <i>Property</i> is an explicitly supported type in Zest™, which makes life a lot easier |
| for everyone involved. |
| </li> |
| <li>The SequenceGenerator has changed the name to "HasSequence", since it doesn't handle the |
| generation of new numbers. It is given <i>Property<Integer></i> to hold the last |
| sequence number, but it doesn't handle the <i>next()</i> equivalent from Evans' code. |
| </li> |
| <li> |
| The increment of the sequence number is instead handled in the SequencingConcern. One |
| advantage is that the number will only be incremented if the policies are met, as we |
| will place this concern at the top of the call chain. |
| </li> |
| <li> |
| Overbooking is a concern (according to Mr Evans in this part of the book) for the |
| <i>makeBooking()</i> method. So, we create an <i>OverbookingConcern</i>, that implements |
| the ShippingService. See below for more details. |
| </li> |
| <li> |
| The ShippingService remains the same. But notice that there is <b>No Implementation!</b> |
| </li> |
| <li> |
| We introduce a new interface, ShippingServiceComposite. This interface binds together the |
| parts to form the Composite. It <b>extends</b> the <i>ShippingService</i> and the |
| <i>Composite</i> and has annotations about how it should be wire together. |
| </li> |
| </ul> |
| |
| <h3>The ShippingServiceComposite</h3> |
| |
| <p> |
| The <i>ShippingServiceComposite</i> declares which concerns should be used, and the order is significant. The |
| <i>SequencingConcern</i> is placed first, that means it will be invoked before the <i>OverbookingConcern</i>, |
| but it performs its own work <b>after</b> the call to the <i>next.makeBooking()</i> method. |
| </p> |
| |
| <h3>The OverbookingConcern</h3> |
| |
| <p> |
| It extends <i>ConcernOf</i> to show which MixinType it is chained into. |
| </p> |
| |
| <h2>Moving on</h2> |
| |
| <p> |
| </p> |
| </body> |
