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Introduction to Model-View-Controller (MVC) Web Programming with TurboGears Leif Oppermann, 24.04.2008

Introduction to Model-View-Controller (MVC) Web Programming with TurboGears Leif Oppermann, 24.04.2008. xhtml x2 css javascript dom, dynamic html java applets cgi/perl php x2 web usability x2 xml x2. Seems incredible complicated, already But still not everything (by far not!)

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Introduction to Model-View-Controller (MVC) Web Programming with TurboGears Leif Oppermann, 24.04.2008

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  1. Introduction to Model-View-Controller (MVC) Web Programming with TurboGearsLeif Oppermann, 24.04.2008

  2. xhtml x2 css javascript dom, dynamic html java applets cgi/perl php x2 web usability x2 xml x2 Seems incredible complicated, already But still not everything (by far not!) How to possibly get it all under one hood? What did you like? WPS - your story so far

  3. Course of this lecture • What is web programming? • What is model-view-controller? • Introducing TurboGears

  4. 1. Web programming • The non-design bits • Developing web applications of all scales • “In software engineering, a Web application or webapp is an application that is accessed with a Web browser over a network such as the Internet or an intranet. Web applications are popular due to the ubiquity of the browser as a client, sometimes called a thin client. The ability to update and maintain Web applications without distributing and installing software on potentially thousands of client computers is a key reason for their popularity. Web applications are used to implement Webmail, online retail sales, online auctions, wikis, discussion boards, Weblogs, MMORPGs, and many other functions.” – Wikipedia.org

  5. Webapps summary • Accessed with a Web Browser (client) • Over a network • Code is mainly run on server • Exception: Javascript (also: Java, Flash,..) • Code is loaded from server • Data is mainly stored on server • Webapps can be updated easily… ..without updating the clients!

  6. General 3 tiered structure • First tier: client side code (web-browser), e.g. (X)HTML, Javascript, Java, Flash • Second tier: server side code, e.g. C/C++, Perl, PHP, Java, Ruby, Python • Third tier: server side database

  7. 2. Model View Controller • Architectural Pattern from Smalltalk (1979) • Decouples data and presentation • Eases the development

  8. Server Client • First thought (ok, but not far enough): • Tier 1: View (Client) • Tier 2: Controller (Server) • Tier 3: Model (Database) Database

  9. Presentation: • View is the user interface (e.g. button) • Controller is the code (e.g. callback for button) • Data: • Model is the database Presentation Data Database

  10. Example Control Flow in MVC • User interacts with the VIEW UI • CONTROLLER handles the user input (often a callback function attached to UI elements) • CONTROLLER updates the MODEL • VIEW uses MODEL to generate new UI • UI waits for user interaction

  11. MVC – general example

  12. 3. Introduction to TurboGears JavaScript Library XHTML template engine Easy to use Python webserver ORM Database Interface (e.g. for MySQL, SQLite, etc.) VIEW CONTROLLER MODEL

  13. 3. Introduction to TurboGears > tg-admin quickstart NewDemo Enter package name [newdemo]: Do you need Identity (usernames/passwords) in this project? [no] [lots of output] > cd NewDemo > ./start-newdemo.py

  14. Let‘s get started by watching a video (20 Minutes Wiki)

  15. So what was that? • Created skeleton files with startup script • Defined Data-Model • created database tables from model • created seeding data in toolbox webapp • Wrote View template in XHTML • Wrote Controller code in Python • Index, edit, save • At this point he had a working system • Several iterations to add all features • Finally wrote AJAX code (Javascript) in template

  16. Benefits • Local development • No need to upload to server • Quick turn around times • No need to compile • As CherryPy watches the file-system and reloads when sources are changed • Database query and update was easy • No need to hand-write SQL • But could be done, if necessary

  17. Summary • Web applications • Client, Server, Database • Easy to maintain, harder to write • Model – View – Controller • Eases web application development • TurboGears • MVC WebApp Framework written in Python • www.turbogears.org

  18. Thanks for your attention • Next lecture: 1 PM today • More on TurboGears (example project) • Movie Collection tool • Questions / Comments: • Now • or email: LXO@CS.NOTT.AC.UK

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