Official ABAP Programming Guidelines

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1 Horst Keller, Wolf Hagen Thummel Official ABAP Programming Guidelines. Galileo Press Bonn

Contents Foreword Acknowledgments ^ ^ 1.1 What Are Programming Guidelines? 17 1.2 Why Programming Guidelines? 18 1.3 Which Guidelines Are Involved Here? 18 1.4 Target Audience 19 1.

2 Contents Foreword Acknowledgments ^ ^ 1.1 What Are Programming Guidelines? Why Programming Guidelines? Which Guidelines Are Involved Here? Target Audience How to Use This Book 20 m 2.1 Separation of Concerns KISS Principle Correctness and Quality 34 lttj 3.1 ABAP Objects as a Programming Model Program Type and Program Attributes Program Type Program Attributes Original Language Modern ABAP Checks for Correctness Syntax Check Extended Program Check Code Inspector ABAP Test Cockpit 76

3 4.1 Source Code Formatting Case Sensitivity Statements per Program Line Using the Pretty Printer Line Width 4.2 Naming Selecting the Language Descriptive Names Names of Repository Objects Program-Internal Names Comments Selecting the Language Content Arrangement in the Source Code Program and Procedure Structure Global Declarations of a Program Local Declarations Source Code Organization Source Code Modularization Multiple Use of Include Programs Alternative Notations Alternative Language Constructs in Statements Chained Statements Method Calls Assignments and Calculations Calculation Expressions Complexity Expressions Nesting Depth Procedure Volume Class Size Dead Code Object-Oriented Programming Encapsulation 156

4 5.1.2 Modularization Static Classes and Singletons Inheritance Class References and Interface References Local Types for Global Classes Instance Constructor 5.2 Error Handling Reaction to Error Situations Classical and Class-Based Exceptions Exception Categories Exception Texts Using Exception Classes Handling and Propagating Exceptions Cleanup After Exceptions Catchable Runtime Errors Assertions Messages User Interfaces Selecting the User Interface Technology Encapsulating Classical User Interfaces Lists Accessibility Datastorage Persistent Data Storage Database Accesses Client Handling Using the Shared Memory Data Types and Data Objects Bound and Standalone Data Types Declaration of Data Types and Constants Declaration of Variables Including Structures Using Types Referring to Data Types or Data Objects Table Work Areas Literals 233

5 6.1.9 Strings Start Values Data Objects for Truth Values Assignments, Calculations, and Other Accesses to Data Assignments Between Different Types Avoiding Invalid Values Using Conversion Rules Specification of Numbers Selecting the Numeric Type Rounding Errors Division by Zero Casting Runtime Errors When Accessing Data Objects Anonymous Containers Passing Global Data by Reference System Fields Access Obsolete and Internal System Fields Evaluation Return Value Using System Fields as Actual Parameters Using System Fields on the User Interface Using System Fields in Operand Positions Internal Tables Selecting the Table Category Secondary Keys Initial Memory Allocation Sorted Filling Aggregated Filling Output Behavior Loop Processing Modularization Units Function Modules and Subroutines Type of the Formal Parameters of Procedures Transfer Type of Formal Parameters Passing Output Parameters by Reference Typing of Formal Parameters Internal and External Procedure Calls Exiting Procedures 302

6 6.5.8 Dialog Modules and Event Blocks Macros Dynamic Programming Techniques Using Dynamic Programming Techniques Runtime Errors During Dynamic Processing Using Dynamic Data Objects Memory Consumption of Dynamic Memory Objects Administration Costs of Dynamic Memory Objects Accessing Data Objects Dynamically Generic Programming Internationalization Storing System Texts Translation-Friendly Message Texts Text Environment Character Set of Source Code Splitting Texts Codepages for Files 337 A Obsolete Language Constructs 341 A.1 Procedures 342 A.2 Declarations 343 A.3 Object Generation 347 A.4 Calls and Exits 347 A.5 Program Flow Control 349 A.6 Assignments 350 A.7 Calculation Statements 352 A.8 Processing Character and Byte Strings 353 A.9 Internal Tables 355 A.10 Dynpro Flow Logic 357 A.11 Classical List Processing 358 A.12 Datastorage 360 A.13 Contexts 362 A.14 External Interfaces 363 B Automatic Check of Naming Conventions 365 B.1 Naming Conventions in the Code Inspector 365 B.2 Type-Specific Prefix Components 366 B.3 Prefixes for Procedure-Local Declarations 367

7 B.4 Structured Programming 369 B.5 Object-Oriented Programming 370 B.6 Assessment of the Naming Conventions 371 C Table of Rules 373 D Recommended Reading 377 E The Authors 379 Index 381

Preface Introduction... 23

Preface Introduction... 23 Preface... 19 1 Introduction... 23 1.1 Releases Used... 23 1.2 New Features in Releases 7.02 and 7.2... 25 1.2.1 New Features in ABAP... 25 1.2.2 New Features in Tools... 28 1.3 Syntax Conventions in The