Facade Pattern

Transcript

1. Façade Pattern • Façade (/fəˈsäd/) = Mask/Veil/Cloak • Hides the ugly stuff
2. Façade Pattern Creational Pattern Structural Pattern Behavioral Pattern Abstract Adapter Command Builder Bridge Interpreter Factory Composite Mediator Prototype Facade Memento Singleton . . . . . The famous 23 design patterns of OOP.
3. Façade Pattern Creational Pattern Structural Pattern Behavioral Pattern Abstract Adapter Command Builder Bridge Interpreter Factory Composite Mediator Prototype Facade Memento Singleton . . . . . Façade = A single class that represents an entire subsystem
4. Façade Pattern • This pattern involves a single class which provides simplified methods required by client and delegates calls to methods of existing system classes.
5. When to use Façade? • A simple interface is required to access a complex system • A system is very complex or difficult to understand • An entry point is needed to each level of layered software • The abstractions and implementations of a subsystem are tightly coupled.
6. jQuery $.get(url, data, callback, dataType); $.ajax({ url: url, data: data, dataType: dataType }).done(callback); // Functions to create xhrs function createStandardXHR() { try { return new window.XMLHttpRequest(); } catch( e ) {} } function createActiveXHR() { try { return new window.ActiveXObject( "Microsoft.XMLHTTP" ); } catch( e ) {} } // Create the request object jQuery.ajaxSettings.xhr = window.ActiveXObject ? /* Microsoft failed to properly * implement the XMLHttpRequest in IE7 (can't request local files), * so we use the ActiveXObject when it is available * Additionally XMLHttpRequest can be disabled in IE7/IE8 so * we need a fallback. */ function() { return !this.isLocal && createStandardXHR() || createActiveXHR(); } : // For all other browsers, use the standard XMLHttpRequest object createStandardXHR; ...
7. Example Engine Body Accessories Model Car