Transcript Teachershare: VBA - Computing At School

Teachershare: VBA
Ilia Avroutine
Royal Grammar School
High Wycombe, Bucks
Bridges the divide between ICT and
Computing
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Start small – with Excel formulas, combining them
Replace them with user functions
Create validation rules
Play with shapes
Add forms and more Visual Basic
Great experience designing interfaces and brings
forward the notion of ergonomics
• Bring on API calls and OOP
Bridges the divide between ICT and
Computing
• Easy syntax, especially if it follows Scratch/Byob and
potentially uses block names as variables/function names
• No semicolons at ends of lines, no cryptic brackets/voids
• Has incredible wealth of information on the Internet
• Can be used to extend the power of Excel for research and
modelling – useful for other subjects and in University
• Pupils can program at home or any computer without
needing to install tricky packages (like JAVA)
• Is similar to Basic in the Open Office – making the skills
multi-platform transferrable, plus similar to Small Basic
• Subs/Functions/Forms/Visual controls/File
Access
• Great to have easy saving in spreadsheets –
great for illustrating arrays
• Supports Records – native support for Access
files via DAO
• Limited OOP support
• Rapid prototyping
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Useful for office employment and automation
Ability to use Windows APIs
Active X controls
The code can write itself – Skynet?
Most skills easily transferrable to other
languages – as our pupils demonstrated,
learning ECMA languages on their own
• Any version of Office should work starting
from Office 2000 – nothing new to install
• Very visual
• Can be extended into ASP, Vbscript
Downsides:
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Slow and verbose
Has no built-in timers (API is a workaround)
Doesn’t indent automatically
More different from pseudocode than Pascal
Is a dead-end language in itself, is quite old-fashioned
No proper OOP inheritance (but there are
workarounds, this is Microsoft, after all)
• Runs on top of an office application
• Requires relaxing Macro protection – potentially, a
security issue
Transition to other languages
• Pupils are encouraged to have a Word file with
accumulation of all the code they’ve written
throughout the years
• We aim to use our VLE Wiki/Glossary feature
to create a repository of code they understand
as it’s at their level
Step 1:
• Logical functions in Excel
• Introduce the concept of pseudocode
• Copying and pasting Excel functions to other
cells substitutes cells’ addresses – brings a
discussion of variables and constants
Step 2: User Defined Functions
• Start easy – a function for converting between metric
and imperial
• Then introduce polynomial functions with conversions
from degrees C to F
• Then test their pseudocode with MPG to Litres/100 km
formula (2/3rds of them usually can’t do it even at this
stage)
• Introduce functions with multiple parameters
• Array functions – great for anybody who uses Excel
anyway
• Generation of random numbers and series – Excel gives
us the ability to plot them – nice and visual
Step 3: Data handling Forms
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Introduction to Modules and Forms
Visual Controls
Variable scope
Proper programming information
Might use forms to extend the User Defined
Function examples done previously
• Use rich content on forms – Google maps, movie
files, mp3 playlists
• Form navigation and interface maps
VBA is not just for programmers
• The industry needs good interface designers,
system architects – all of these concepts can
be easily taught in VBA without getting
bogged down with “proper” programming
which might put some of the weaker pupils off
Using Office shapes for modelling
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Railroad crossing
LCD multi-segment digits
Pong
Cash Machine
Battleship
Under development: Pacman, Space Invaders,
Arkanoid, etc.
Forms can also be used for games
• Pupils will face some of the same limitations
as the early designers in 1970s – no strong
graphics, so have to use very basic objects
Agenda
• Rock, Paper, Scissors game via 2 random
number generators
– Discussion of pseudocode for the machineaccessible rules of winning
– Use Excel formulas (Lookup, IF)
– Show equivalent VBA function
• MPG to Litres per 100 Km conversion
– Discussion of pseudocode
– Implementation
Temperature Conversion (from
http://www.plvwtelco.net)
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Convert Fahrenheit to Celsius
1.Determine the temperature in Fahrenheit
2.Using your calculator, subtract 32
3.Multiply the result times 5
4.Divide that answer by 9
5.Your final answer is the temperature in Celsius
For the math purist, the formula is (F-32)*5/9 = C
No calculator handy? Take Fahrenheit, subtract 30, then divide by 2
Convert Celsius to Fahrenheit
1.Determine the temperature in Celsius
2.Using your calculator, multiply the temperature times 1.8
3.Add 32 to the result
4.Your final answer is the temperature in Fahrenheit
For the math purist, the formula is (C*1.8)+32=F
No calculator handy? Take Celsius X 2, then add 30
VBA at a glance (assuming Office 2007 but others will
work, just different screens) A spreadsheet is a
giant 2D array (3D
if you consider
using multiple
sheets)
VBA gives pupils
access to all
maths functions
of Excel directly
Also – full access
to graphics
abilities for
plotting and
tabulation
VBA is hiding behind ALT+F11 or...
Now, your Excel has Developer menu
that you can use to enable Macros
Make sure that Macros are enabled
Macro viruses are no
longer a threat with
new version of MS
Office, so you should
be ok. Nothing
replaces a proper
antivirus program
VBA Editor window
Familiar VB syntax – so, can leverage
all the VB literature
The new bits – VBA objects, right-click this
area to add Code modules and Forms
VBA objects:
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Workbooks
Sheets
Shapes
Forms
Ranges (cells)
Any ActiveX object – from Quicktime video to
Flash movie
• Use Macros to explore VBA objects
Here is a simple example – a user defined
function converting centimetres to inches
Give it a meaningful name. You can
have as many as you like
The function code itself... Functions
take parameters and are typed
Function cm2inch(ByVal inputCM As Single) As Single
cm2inch = inputCM / 2.54
End Function
The moment you are finished coding the function, you
can switch back to the spreadsheet view and Excel will
recognize your function and add it to its built-in list
Behaves just like native
functions and takes a cell
that you click on as a
parameter
Function cm2inch(ByVal inputCM As Single) As Single
cm2inch = inputCM / 2.54
End Function
The result, with some extra formatting
Something a bit more involved. VBA being partially
OOP, we have arrays(1st function) and also
collections(2nd function below)
Function sumOfCubes(ParamArray otherElements() As Variant)
Dim counter As Integer
For counter = 0 To UBound(otherElements)
sumOfCubes = sumOfCubes + otherElements(counter) ^ 3
Next counter
End Function
Function sumOfCubes2(ByVal otherElements As Range)
Dim element As Range
For Each element In otherElements.Cells
sumOfCubes2 = sumOfCubes2 + element ^ 3
Next
End Function
That’s it for the intro into VBA. Some
very good links
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http://www.cpearson.com
VBA in a Nutshell
VBA for Engineers
Excel Archives
Windows API list
10 VBA Tips from Microsoft
Interacting with Access Databases
General Excel and VBA resources