The connections between UI components and related objects could be extremely complex. Object-oriented programming distributes functionalities among objects. This makes coding easier with cleaner and more intuitive logic; however, it does not ensure the reusability and sometimes makes it difficult to understand if you look at the code again after some days (you may still understand every single operation but would be confused about the interconnections if the network becomes really intricate).

Consider a page for editing user profile. There are standalone inputs like nickname and tagline, as well as inputs that are related to each other. Taking location selection for example, there could easily be a tree-level location and the options available in lower levels are determined by the selection of higher levels. However, if those objects are managed directly by a single huge controller, it will result in a page that has limited reusability. The code formed under this situation...