Mimesis and Compositing SWING

Lecture 17, Oct 27 2009

Administrivia

•Reminders:

•Quiz 2 on Thurs

•Have your P3 groups ready by Thurs

•If you don’t pick them, I will...

Progress or Congress?•Last time:

•Micro-tests

•MVC reprised; MV implementation

•DebugLog

•Today:

•Words to the wise: user input validation

•Design principle: mimesis

•UIs in SWING

•The Composite design pattern

http://xkcd.com/327/

Words to the wise...

Design Principle o’ the Day

Principle of mimesis: Make the structure of your code mirror the structure of the thing that you are representing.

Mimesis

•Real world has already solved design problem once

•A solution exists; steal it where you can

•Exploits human visualization/reasoning capabilities

•Improves self-documentation

•Sometimes worth introducing objects that exist only to name conceptual things

Mimesis: examples

•Project 2:

CustomerType

EmployeeType

World

Receipt

Plant

AssemblyLine

Mimesis: corollary 1

•Verbs are things too...

Event.execute()

Dispatcher.dispatch()

OrderContainerFactory.newOrderContainer()

Mimesis: corollary 2

•If the thing is completely abstract (no “real world” counterpart)

•Make up a visual process for it

•Then mimic that...

Mimesis: corollary 2

•If the thing is completely abstract (no “real world” counterpart)

•Make up a visual process for it

•Then mimic that...

•Example: P1 design

•Based on thinking about clerks at the census bureau

Application: SWING

•SWING designed to be modular

•“glue together” components

•Massive PITA to write GUI code by hand

•Can become a real morass of spaghetti code and/or immense method bodies

•Instead, make structure of GUI code mimic structure of the display

configFrame

The Viz configuration

configPanel

plantViz

plantButtons

The Viz configuration

exptConfig

plantEmplViz

lineBuilderViz

assemblyLineViz

Object Reference Hierarchy

Code goes the same way..._configFrame.add(_buildConfig());

private Component _buildConfig() {final JPanel result=new JPanel();result.add(new PlantViz());result.add(_buildPlantButtons());return result;

}

public class PlantViz extends JPanel {public PlantViz() {super();this.add(_buildExptConfig());this.add(_buildPlantEmployeeViz());this.add(_buildLineViz());

}

Another Design Pattern

•So why does this nested design work?

•Why can we get away with stuffing widgets (JPanel, JScrollPane, JButton, etc.) inside other widgets (JPanel, JScrollPane, etc.) willy-nilly?

•Composite Design Pattern

Composite•Problem to solve:

•Conceptual containers (JPanel, JScrollPane)

•Conceptual “leaf” widgets (JButton, JTextArea)

•Part-whole structure

•Want the code to treat both uniformly

•Don’t want to have to distinguish between leaf and container in client code

Composite in SWING

General Composite Pattern