Sencha has also launched support for the MVC-like (Model View Controller) pattern. MVC allows a developer to seperate the user interface (the view) from the data (the model) and orchestrate the interaction between the two (the controller). With that separation of responsibilities in place, a developer can iteratively enhance the view or model and add more application logic to the controller as needed. The approach also allows prototypes to be presented relatively quickly and then rapidly enhanced to production code. Sencha says it has introduced MVC to help standardise architecture patterns for larger development teams to make it easier for developers to "get up to speed" as they move between projects.
A new class system is intended to help developers, for example, to detect dependencies. Ext JS 4 also allows the library to run in a sandbox for the first time. Different versions of Ext JS can therefore be run on one page without colliding. Other revisions were made to the grid components, which are now modular and able to support "infinite" amounts of data without paging, and in support for themes, which now use stylesheet language Sass (syntactically awesome stylesheets) and CCS meta-framework Compass. For an overview of these and additional changes, see "What's new in Ext JS 4".