LECTURE 4:VALIDATING YOUR DESIGN

MKT 101 – Introduction to Marketing

Why should I learn about

marketing?I’m in CSC to avoid

this!

Today’s Goal

Learn to validate & fix designs before coding What matters in comments & how these

can help Techniques & tricks to avoid writing useless

code Javadoc v. regular comments: why have

both? Why both types of comments rely on

marketing Why is this vital for testing the proposed

solution?

Today’s Goal

Learn to validate & fix designs before coding What matters in comments & how these

can help Techniques & tricks to avoid writing useless

code Javadoc v. regular comments: why have

both? Why both types of comments rely on

marketing Why is this vital for testing the proposed

solution?

Weeks of coding makes up for minutes of planning

Time Required To Understand

Atte

ntio

n Pa

idHow My Homies Roll

Already made#YouSuck

a trending topic

Time Required To Understand

Atte

ntio

n Pa

idHow My Homies Roll

Reactions to Your Code

Time Spent

Use

r’s

Abili

ty

Passion Threshold

Suck Threshold

Reactions to Your Code

Time Spent

Use

r’s

Abili

ty

Assembly Code

Java

Passion Threshold

Suck Threshold

Reactions to Your Code

Time Spent

Use

r’s

Abili

ty

Assembly Code

Java

Passion Threshold

Suck Threshold

Making people think is preying on their weakness Explicitly state details needed to use code

People will assume that everything has purpose Male nipples, appendix, Matt still talked

about If it serves no purpose, why would it be

created? Guessing game created from unused

parameters Don't make user probe what return value

means

Intuitive Is Key

Making people think is preying on their weakness Explicitly state details needed to use code

People will assume that everything has purpose Male nipples, appendix, Matt still talked

about If it serves no purpose, why would it be

created? Guessing game created from unused

parameters Don't make user probe what return value

means

Intuitive Is Key

It returned 5.

What the $#&@#* does 5

mean?

Making people think is preying on their weakness Explicitly state details needed to use code

People will assume that everything has purpose Male nipples, appendix, Matt still talked

about If it serves no purpose, why would it be

created? Guessing game created from unused

parameters Don't make user probe what return value

means

Intuitive Is Key

I DEFINITELY

need another drink…

What To Do With Your Design

Move on to next step: write your javadoc Validate your thinking by forcing

communication Performs test that you are clear what

method does Team development easier, since method

use known If done well, will find helps develop 1st test

set

What To Do With Your Design

Move on to next step: write your javadoc Validate your thinking by forcing

communication Performs test that you are clear what

method does Team development easier, since method

use known If done well, will find helps develop 1st test

set

But We Cannot Document Yet!

Of course, do not yet know details such as… How method is coded or calls it makes Which of the class’s fields used within

method How it computes result to get return value Given an input, why specific algorithm used

javadoc does NOT need & should not include it You may (or should be asking yourself):

Why?

Why Not Include Details?

You write code once… This is goal, idea is to solve problems not

write code Writing code is work & laziness means

minimizing this Once code bug free, do not want to look at

it again …but read comments often

If javadoc duplicates code, could just read code

Only provide what users need

Why Not Include Details?

You write code once… This is goal, idea is to solve problems not

write code Writing code is work & laziness means

minimizing this Once code bug free, do not want to look at

it again …but read comments often

If javadoc duplicates code, could just read code

Only provide what users need

What Should Comments Say?

javadoc works with design & does not repeat it For each class what instances do & where to

use What a method does & when it should be

called Given a methods actions, what method’s

results are Meaning of return values & any special

“magic” values For each real error: when exception will be

thrown How to call method including examples

(with return)

Good javadoc

/** * Perform the basic work needed when a button is * pushed. This will illuminate the light in the * button. The first time a button is hit it will * also send a message to the elevator controller. */public void pushButton() { /* Code goes here… */ }

How Does javadoc Test Design? What if do not know enough to write javadoc? Can you write code you cannot describe

what it does?

How Does javadoc Test Design? What if do not know enough to write javadoc? Can you write code you cannot describe

what it does?Hint:

How Does javadoc Test Design? What if do not know enough to write javadoc? Can you write code you cannot describe

what it does?Hint:

YourDesignSucks

DonkeyBalls

Is This Method Really Usable?

Is This Method Really Usable?

What is the Goal Again?

Javadoc != Java and should not be confused If comments are good, easier to understand

than Java Only details users need to use method or

class For this to work must make sell its simplicity Show important connections to well-known

examples@see class @see #method @see class#method Explicitly state any "magic" param or return

values Provide examples to clarify how it will work

Now This I Can Use

Now This I Can Use

Now This I Can Use

Other Details To Describe

State all assumptions to prevent future bugs When calling this method, what else will

happen?

Other Details To Describe

State all assumptions to prevent future bugs When calling this method, what else will

happen? Any assumptions upon which method relies

Other Details To Describe

State all assumptions to prevent future bugs When calling this method, what else will

happen? Any assumptions upon which method relies Once method completes, details needed for

later

Programming By Contract

Precondition true at start when method called Ensuring these met responsibility of calling

method Postconditions true at end of the

method call Guaranteeing this responsibility of called

method Only if preconditions met must this

happen, however

Programming By Contract

Precondition true at start when method called Ensuring these met responsibility of calling

method Postconditions true at end of the

method call Guaranteeing this responsibility of called

method Only if preconditions met must this

happen, however

Good Javadoc Example

/** * Perform the basic work needed when a button is * pushed. This will illuminate the light in the * button. The first time a button is hit it will * also send a message to the elevator controller.<br/> * * Precondition: lit.isOff(); controller is set<br/> * * Postcondition: !lit.isOff() && * request sent to elevator controller */public void pushButton() { }

What's Next?

Could start to write code at this point in project But doing this means still may find many

bugs Fixing these hard if calling many other

methods Ideal if we could 1st check that method

actually works Remember key trait of successful

programmers

Successful Programmers

Could start to write code at this point in project But doing this means still may find many

bugs Fixing these hard if calling many other

methods Ideal if we could 1st check that method

actually works Remember key trait of successful

programmers

Outlining a Method

Write pseudocode outline of how method works Can be written assuming other methods

they work Can ignore coding details, so simpler &

easier to write Once done writing, tests check

algorithm works Fix errors BEFORE coding to limit

debugging needs Can then make the algorithm into

comments Check code against comment, since that

passed tests Plain English description makes reading

code easier

Outlining a Method

How to write algorithm: what details important? Can skip punctuation of any sort: this is

not code Should include major loops, but can write in

English Important to translate: each action to take

is explicit Can write “swap values” or group

assignments Using shorthand fine, but translation to

code clear

Pseudocode Needs More Detail

Pseudocode Needs Less Detail

Heated Handlebars

Heated Handlebars

For Next Lecture

Week #2 homework available on Angel page Due by 5:00PM Tuesday Submit assignment via e-mail & (possibly)

paper Reading for Friday linked to from Angel

schedule Discuss range of possible tests to perform How often to test code as we are writing it Present methods of handling failed test