Sublime Deslimer: Refactoring with Confidence using RDi - Edmund Reinhardt - RDi architect - Gateway/400 Group
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Sublime Deslimer:
Refactoring with Confidence
using RDi
Edmund Reinhardt – RDi architect
© 2018 IBM Corporation
Why does it matter if code is slimy
• Could kill your company
– Cautionary tale of Sword Inc
– Was the market dominating C debugger in the 80s
– But were never successful in getting a C++ debugger out
– Went bankrupt as a result
– Code was rushed to be first to market
– Never time to clean up
– And then when the C++ requirement came up,
• Took too long to update code
• Code was buggy and performed poorly
Some anecdotes and thoughts learned from Robert Martin in Clean Code
© 2018 IBM Corporation
How does code get slimy
• In the beginning the code is clean and it is easy to enhance
• Over time the code gets messy but no time to fix
Productivity over time
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© 2018 IBM Corporation
Business IMPACT
• This creates a gap between business plans and breaks promises to customers and loses profit
Projected Plan vs Real Productivity
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Productivity Business Plan
© 2018 IBM Corporation
Mythical Man Month MAKES it WORSE
• “adding manpower to a late software project makes it later” - Frederick Brooks Jr
• The old software is teaching the new programmers. And so even after the learning curve is conquered,
productivity is still steadily declining.
• But in the mean time the cost is going up as a step function
Plan vs Productivity vs Cost
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Theoretical 90
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Productivity after 70
adding people 60
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Productivity Business Plan
Cost
© 2018 IBM Corporation
The big redesign in the sky
• Solution according to programmers
– The ones who know – unlike the managers
• Need to start over – green field
• In the absence of solid test suite, all of the requirements locked in old code
• But in the mean time, need a solution for customers
• One team repairing the old system while “Seal Team 6” writes new
• Xenos paradox
• If rewrite involves a new platform then it is not a tortoise being chased
– Rather a Ferrari out of gas being pushed by its driver
• Bottom line: Cannot run away from your bad code
© 2018 IBM Corporation
Solution: Refactoring
• Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal
structure without changing its external behavior. Its heart is a series of small behavior preserving
transformations. Each transformation (called a 'refactoring') does little, but a sequence of
transformations can produce a significant restructuring. Since each refactoring is small, it's less likely to
go wrong. The system is also kept fully working after each small refactoring, reducing the chances that
a system can get seriously broken during the restructuring.
– Martin Fowler at refactoring.com as cited in: Lawrence Bernstein, C. M. Yuhas (2005) Trustworthy
Systems Through Quantitative Software Engineering. p. 266
© 2018 IBM CorporationGoal of Software
• Communicate
– (a) with computers
– (b) with humans
• “Any fool can write code that a computer can understand. Good programmers write code that humans
can understand.”
– Martin Fowler 2009
• “Clean code is simple and direct. Clean code reads like well-written prose. Clean code never obscures
the designer's intent but rather is full of crisp abstractions and straightforward lines of control.” - Grady
Booch
• ”Clean code can be read, and enhanced by a developer other than its original author. It has unit and
acceptance tests. It has meaningful names” – David Thomas
© 2018 IBM CorporationExcuses
• My manager/customer can’t wait – so I have no time and have to rush this
• I can always go back and clean it later
• Yeah right! When is the last time you went back and cleaned it later?
© 2018 IBM CorporationNames
• Names are critical to
– Revealing the programmer’s intent
– Making the code read like prose
• That’s why RDi made renaming the first refactoring that we
are making available
• Since the tool makes renaming easy and error-free there is
no excuse to tolerate cryptic or out-of-date names any more
© 2018 IBM Corporation11
Rename ILE RPG Declaration Refactoring
• RPG refactoring was the highest voted RFE in 2016
• Refactoring is the process of changing code without changing the function of the code. The
purpose of refactoring is to make the code more readable and maintainable.
• Rename refactoring allows the user to rename all and only the symbols in an ILE RPG file that
are related to the user-defined name containing the cursor or selection.
• This works for any user-defined name including file, record format, standalone variables, data
structures, subfields, procedures.
• It works within fixed, free and fully free (**FREE) source.
© 2018 IBM Corporation12
Rename Refactoring – Invocation
•Place the cursor or select the name to rename in the Remote Systems LPEX editor.
•Either right click or pull down the Source menu and select Refactor->Rename, or press
Alt+Shift+R.
•If the name is not a valid user-defined name, the Source->Refactor->Rename will be disabled
© 2018 IBM Corporation13
Rename Refactoring – Specify new name
• After selecting the menu item, a dialog will appear prompting for the new name.
• The OK and Preview buttons will only enable once the new name is different than the old
one.
• Click OK to complete the process, click Preview to preview the changes that will occur, or
select Force preview and then OK to ensure that the changes are previewed.
– If you select Force preview, this option will become the default for the next time that you
use the wizard.
© 2018 IBM Corporation14
Rename Refactoring – Preview
• The initial preview panel shows how many references there are to the declaration that you
want to rename in an informational message.
• If there are issues with the rename, warning or fatal messages will be shown. If fatal
messages, only Back and Cancel buttons are available.
© 2018 IBM Corporation15
Rename Refactoring – Preview
• Preview shows the changes that will be made before you apply them to the editor.
© 2018 IBM Corporation16
Rename Refactoring – Preview
• Expand the list of previewed changes to work with changes individually. Clear the checkbox if
you do not want a specific change to be performed.
© 2018 IBM Corporation17
Rename Refactoring
• Click OK to update the editor.
• Use Undo if you want to revert the changes.
• Limitations
– /COPY members are not updated.
– Code that is excluded by /IF /ELSE statements will not be renamed.
– Only renames within a line are supported
• Documentation available at:
https://www.ibm.com/support/knowledgecenter/SSAE4W_9.5.1/com.ibm.etools.iseries.rse.doc/topics/refactor.html
© 2018 IBM CorporationRename with confidence!
• Much more sophisticated than find/replace
• Detects
– Overflowing fixed columns
The renamed "qual.p(y):qual.b" will overflow positions 12-25 of line 16 :
" C [q.p(y):q.b ]scan x:q.q(q.b) q.q(q.b) 10 “
– Same name as external definitions
– When RPG language makes it ambiguous (EXTNAME parm is a literal)
© 2018 IBM CorporationQualified Subfields
© 2018 IBM CorporationExample: Hex converter
© 2018 IBM CorporationCatching up to 1994
• Clearly your first goal will be get to ILE RPG
– Can always use CVTRPGSRC or partner tools from ARCAD or Linoma
Hurray!, 10 character names, no indentation, still in fixed form jail
© 2018 IBM CorporationConvert to free form
Hurray! Indented free form, lots of room for long names, but who is going to make them long?
© 2018 IBM CorporationAAS (e-config) - PID 5733-AC1
Convert fixed RPGLE to modern RPG Free Form
Before and after –
Modernization of source code using
ARCAD RPG Converter
Now conveniently available through
AAS (e-config) –
PID 5733-AC1
© 2018 IBM CorporationFree form necessary but not sufficient
• While converting to free form ILE, now communicates the structure
– Especially if you fix indentation using Ctrl-Shift-F (in RDi)
• It does not fix the names
• If your code is like well-written prose you will not need comments
• For example why have
• When you could have
• Not only is the comment less informative than the code
• But every call reads like well-written prose
– Well almost – we have to convert to procedure to avoid the EXSR
© 2018 IBM CorporationUsing RDi to refactor slimy code (names)
© 2018 IBM CorporationNaming rules
• Choose your names thoughtfully
• Communicate your intent
• Avoid disinformation
• Pronounceable names
• Avoid Encodings
• Choose parts of speech well
– Variables are nouns
– Subroutines/Procedures are verbs
– Indicators/Procedures returning indicator are predicates like is or has
© 2018 IBM CorporationLength of Names - Scope rule
• If in tiny scope, use short names
• If in large/global scope, use long names
• Opposite for Procedures
© 2018 IBM CorporationWhat makes your code slimy
• Stench
– you can tell how bad the code is by the expression on the face of the
programmer who pulls it up on the screen
• Rigidity = The tendency of a system to resist change
– Requires many changes to many different places to make
improvement
• Fragility
– Malfunctions in many unpredictable ways when a simple change is
made
• Inseparability
– When the various parts of that system cannot be independently reused
in another system
• Opacity = cannot understand the intent by reading the code
• Example
– The 1 line change that wasn’t
© 2018 IBM CorporationRefactoring – Procedures and Scope
© 2018 IBM CorporationWhen a name is not just a name
© 2018 IBM CorporationSoftware Engineering Principles
• Use modern language
– Move to ILE and move to free form
• Use modern tools
– An IDE can help you understand and transform your code intelligently
– We trust computers to help diagnose cancer, detect fraud, catch criminals, do taxes
• Surely it can help us understand/transform computer programs
• Make your code understandable
– Nomenclature
– Structure
• Make your code verifiable
– Test driven development
– See tomorrows talk 31CA Test Driven Development – best practices applied to IBM i
• at 8AM in Salon A
© 2018 IBM CorporationMore Refactoring with RDi – step by step – Ted Holt
• https://www.itjungle.com/2018/04/16/guru-rdi-and-refactoring/
• https://www.itjungle.com/2018/05/07/guru-refactoring-into-routines/
• Check them out!
© 2018 IBM CorporationFor More Information:
Some Links You Need Twitter #Hashtags
IBM i Home Page:
www.ibm.com/systems/i #IBMi30
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IBM 30th Anniversary @IBMSystems #IBMi
http://ibmi30.mybluemix.net/ @COMMONug #IBMAIX
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License Topics: #BigData
https://www-01.ibm.com/support/docview.wss?uid=nas8N1022087
© 2018 IBM CorporationFor More Information:
Blogs
IBM Blogs:
• IBM Systems Magazine You and i (Steve Will) http://ibmsystemsmag.com/blogs/you-and-i/
• IBM Systems Magazine i-Can (Dawn May) http://ibmsystemsmag.com/blogs/i-can/
• IBM Systems Magazine: Open your i (Jesse Gorzinski) http://ibmsystemsmag.com/blogs/open-your-i/
• IBM DB2 for i (Mike Cain) http://db2fori.blogspot.co.uk/
• IBM DB2 Web Query for i (Doug Mack) http://db2webqueryi.blogspot.co.uk/
IBM Champion’s Blogs:
• IBM Systems Magazine: iDevelop (Jon Paris and Susan Gantner) http://ibmsystemsmag.com/blogs/idevelop/
• IBM Systems Magazine: iTalk with Tuoy http://ibmsystesmag.com/ibmi/trends/italk-with-tuohy/
© 2018 IBM CorporationYou can also read
