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A comment on comments

We learn in school that all code should have comments. Then, in real life, we find that not everyone was paying attention to what was said in school. As a consequence, most code is obscure and without proper comments.

I was always careful to comment every relevant step of my code, specially the parts which are obscure or not self-explanatory.

But since I recently read Uncle Bob‘s Clean Code, my opinion on this changed. Today I believe that the less comments the better. And yet, I don’t see this as contradictory to what I used to think.

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ABAP, the lobotomizer

João studies Computer Science at his College where he learns Java, polymorphism, encapsulation and a lot of other programming techniques and best practices. When he graduates, he decides to join a company to work in SAP. At the introduction training which his new company offers, the first thing he learns is how to make a program in ABAP. Here’s how they teach it:

“Go to transaction SE38, create program ZJOAO and then create includes ZJOAO_TOP, ZJOAO_FRM and ZJOAO_SEL. You declare all variables in _TOP, the selection screen you put in _SEL and all the FORMS must go into _FRM. Then write START-OF-SELECTION and under that put all the SELECTs and finally write END-OF-SELECTION and there you show the results in an ALV. It’s that simple. Welcome to ABAP.”

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Serialization – Clone Dolly in ABAP

A ovelha Dolly

This article was written by José Vília:

The Dolly sheep was alive in ABAP and I didn’t know about it.

Having created a class instance, I’d like to share it with another totally independent program to use it as if the instance had been created there.

It’s an ABAP Dolly sheep factory we’re talking about here, people. Serialization in the ABAP world.

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ALV Grid built in error protocol

We’re all lazy. It’s just human. Programmers are human. We’re often lazy when it comes to the way we program something. And usually being lazy when making a program will result in someone else having more work when maintaining it.

Let he who is free of laziness throw the first rock.

I won’t!

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PlantUML – Finally UML became simple to use

Foreword

When I say that I like to use UML class diagrams to document my code, people think I’m crazy.

Introduction

The UML has gained a bad reputation because people think that, first you make the classes diagram in UML and only then write the program. But that was in 1996, when you the good practices said the first thing to do was the whole technical spec, even if no one really did it.

Nowadays, fortunately, we are no longer ashamed to say that the very act of programming is already in itself a way of drawing.

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ASSERT vs Exception

If you read Abapinho you already know how much I like exception classes. But this is not the only ABAP mechanism for dealing with errors.

There is another one, called ASSERT, which should be used more often.

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Get the deepest text of chained exceptions

If you’re not already using ABAP Objects you’re chicken.

If you use them, I do hope you’re following the best practice of using class exceptions.

And if you’re using class exceptions you better understand the best way of using them, particularly the advantages of chaining them.

This said, here’s what brings us here today. In the post about chained exceptions I showed a way to get the text of the deepest exception in the chain by using a WHILE loop:

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How to not screw up when returning a REF TO DATA

I’ve been using more and more references in ABAP.

I used to use REF TO only for classes but I’ve been finding more and more advantages in using them for other data types. But, just like in C++, care must be used when dealing with data references. Things can easily go very wrong.

In this article, I’ll try to show you how to use and how not to use REF TO DATA. Let’s start by an example of how not to do it.

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Local $PACKAGES

Any object created in SAP must belong to a package.

Until recently, whenever I needed to create a program for a quick test I’d put it in the $TMP package. This way I was sure that it would never be transported to another system.

But sometimes I have the need to create stuff in the development system which, even though it should never be transported, should stay there forever. For example, development tools like ZSAPLINK and abapGit. But if we put everything under package $TMP it will soon be a big mess.

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INSERT wa INTO itbl REFERENCE INTO ref. Bug?

Every day I use more reference variables in ABAP. First I used REF TO just for classes but, as I become more familiarized with its advantages, I start using them more and more for data structures, instead of field-symbols.

But I recently found na unfortunate behavior of the following command:


INSERT wa INTO itbl REFERENCE INTO ref.

Let me give you some context before I complain about it.

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We should be accountable for the crap we make

If, when building a bridge, a civil engineer makes a mistake in one of the calculations, the bridge falls. But the bridge won’t fall alone. Most probably that engineer will also fall with it. He is accountable for what he did because he must sign his projects.

ABAP programmers don’t have that kind of problems.

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GROUP BY in LOOPs on internal tables

We’ve all sorted internal tables to use AT NEW on a LOOP.
But starting from 7.40, we can use GROUP BY on LOOPs.

The ability to group by values based on expressions or even methods is great.

The grouping is done on the first LOOP and can be processed afterwards. Try running the code below and I bet you’ll be as impressed as I was.

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In ABAP’s name, I baptize you

When we learn ABAP, we are taught a series of rules on how to name variables. Not everyone uses the same rules but, still, some strict rules are shared between many people:

  • Local variables must start with L: L_BUKRS;
  • Global variables must start with G: G_MODE;
  • Internal tables must have T_: LT_MARA;
  • Structures must have S_: LS_MARA;
  • Object references must have R_: R_CUSTOMER;
  • input parameters must start with I, output with O, changing with C and returning with R.
  • And the most stupid of all, field-symbols must start with FS_: <FS_MARA>.

In the early XXI century those rules made some sense (except for the field-symbols on, which was, and still is, as stupid as writing ‘pencil’ in all our pencils). Today they don’t make much sense anymore. Let me explain.

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CONCATENATE LINES OF itbl

If you want to serialize a set of strings stored in an internal table there are two ways to do it. One is dull, the other one is full of style.

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Modify one field in all lines of an internal table

What I’m about to show you is not exactly new. It has even been used in Abapinho before. But since there is still a lot of people out there using LOOP to change a single field of an internal table, I thought it would be worth talking about it.

Say you have an internal table with one million and two hundred thousand entries and want to change the field ICON so that it has ‘@FM@‘ in all lines.

Instead of doing this:


LOOP AT lt_data ASSIGNING <data>.
  <data>-icon = '@FM@'.
ENDLOOP.

Try doing this instead:


ls_data-icon = '@FM@‘.
MODIFY lt_data FROM ls_data TRANSPORTING icon WHERE icon <> ‘DONALD DUCK’.

You can obviously replace the condition value with any other Disney character.

Thank you Sérgio Serra for suggesting that it could be interesting talking about this.
Thank you Andrew Becraft for the photo.

Greetings from Abapinho.


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