1 Introduction

17

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

1.5 How to Use This Book

20

2 General Basic Rules

23

2.1 Separation of Concerns

23

2.2 KISS Principle

32

2.3 Correctness and Quality

34

3 ABAP-Specific Basic Rules

41

3.1 ABAP Objects as a Programming Model

41

3.2 Program Type and Program Attributes

50

3.2.1 Program Type

51

3.2.2 Program Attributes

55

3.2.3 Original Language

60

3.3 Modern ABAP

62

3.4 Checks for Correctness

65

3.4.1 Syntax Check

65

3.4.2 Extended Program Check

69

3.4.3 Code Inspector

72

3.4.4 ABAP Test Cockpit

76

4 Structure and Style

79

4.1 Source Code Formatting

80

4.1.1 Case Sensitivity

80

4.1.2 Statements per Program Line

84

4.1.3 Using the Pretty Printer

86

4.1.4 Line Width

89

4.2 Naming

91

4.2.1 Selecting the Language

92

4.2.2 Descriptive Names

94

4.2.3 Names of Repository Objects

101

4.2.4 Program-Internal Names

106

4.3 Comments

115

4.3.1 Selecting the Language

115

4.3.2 Content

117

4.3.3 Arrangement in the Source Code

120

4.4 Program and Procedure Structure

123

4.4.1 Global Declarations of a Program

124

4.4.2 Local Declarations

127

4.5 Source Code Organization

130

4.5.1 Source Code Modularization

130

4.5.2 Multiple Use of Include Programs

132

4.6 Alternative Notations

135

4.6.1 Alternative Language Constructs in Statements

135

4.6.2 Chained Statements

137

4.6.3 Method Calls

141

4.6.4 Assignments and Calculations

143

4.6.5 Calculation Expressions

145

4.7 Complexity

146

4.7.1 Expressions

147

4.7.2 Nesting Depth

149

4.7.3 Procedure Volume

150

4.7.4 Class Size

151

4.7.5 Dead Code

153

5 Architecture

155

5.1 Object-Oriented Programming

155

5.1.1 Encapsulation

156

5.1.2 Modularization

157

5.1.3 Static Classes and Singletons

161

5.1.4 Inheritance

166

5.1.5 Class References and Interface References

167

5.1.6 Local Types for Global Classes

169

5.1.7 Instance Constructor

171

5.2 Error Handling

172

5.2.1 Reaction to Error Situations

172

5.2.2 Classical and Class-Based Exceptions

174

5.2.3 Exception Categories

178

5.2.4 Exception Texts

180

5.2.5 Using Exception Classes

183

5.2.6 Handling and Propagating Exceptions

185

5.2.7 Cleanup After Exceptions

186

5.2.8 Catchable Runtime Errors

188

5.2.9 Assertions

190

5.2.10 Messages

191

5.3 User Interfaces

195

5.3.1 Selecting the User Interface Technology

195

5.3.2 Encapsulating Classical User Interfaces

199

5.3.3 Lists

204

5.3.4 Accessibility

207

5.4 Data Storage

208

5.4.1 Persistent Data Storage

208

5.4.2 Database Accesses

210

5.4.3 Client Handling

211

5.4.4 Using the Shared Memory

213

6 Secure and Robust ABAP

217

6.1 Data Types and Data Objects

217

6.1.1 Bound and Standalone Data Types

218

6.1.2 Declaration of Data Types and Constants

220

6.1.3 Declaration of Variables

224

6.1.4 Including Structures

226

6.1.5 Using Types

228

6.1.6 Referring to Data Types or Data Objects

230

6.1.7 Table Work Areas

232

6.1.8 Literals

233

6.1.9 Strings

236

6.1.10 Start Values

238

6.1.11 Data Objects for Truth Values

239

6.2 Assignments, Calculations, and Other Accesses to Data

241

6.2.1 Assignments Between Different Types

241

6.2.2 Avoiding Invalid Values

243

6.2.3 Using Conversion Rules

245

6.2.4 Specification of Numbers

247

6.2.5 Selecting the Numeric Type

249

6.2.6 Rounding Errors

253

6.2.7 Division by Zero

255

6.2.8 Casting

255

6.2.9 Runtime Errors When Accessing Data Objects

257

6.2.10 Anonymous Containers

259

6.2.11 Passing Global Data by Reference

260

6.3 System Fields

262

6.3.1 Access

262

6.3.2 Obsolete and Internal System Fields

264

6.3.3 Evaluation

265

6.3.4 Return Value

267

6.3.5 Using System Fields as Actual Parameters

268

6.3.6 Using System Fields on the User Interface

270

6.3.7 Using System Fields in Operand Positions

272

6.4 Internal Tables

273

6.4.1 Selecting the Table Category

274

6.4.2 Secondary Keys

276

6.4.3 Initial Memory Allocation

280

6.4.4 Sorted Filling

281

6.4.5 Aggregated Filling

283

6.4.6 Output Behavior

284

6.4.7 Loop Processing

286

6.5 Modularization Units

287

6.5.1 Function Modules and Subroutines

288

6.5.2 Type of the Formal Parameters of Procedures

289

6.5.3 Transfer Type of Formal Parameters

292

6.5.4 Passing Output Parameters by Reference

294

6.5.5 Typing of Formal Parameters

296

6.5.6 Internal and External Procedure Calls

298

6.5.7 Exiting Procedures

302

6.5.8 Dialog Modules and Event Blocks

304

6.5.9 Macros

306

6.6 Dynamic Programming Techniques

309

6.6.1 Using Dynamic Programming Techniques

309

6.6.2 Runtime Errors During Dynamic Processing

311

6.6.3 Using Dynamic Data Objects

313

6.6.4 Memory Consumption of Dynamic Memory Objects

315

6.6.5 Administration Costs of Dynamic Memory Objects

318

6.6.6 Accessing Data Objects Dynamically

321

6.6.7 Generic Programming

324

6.7 Internationalization

329

6.7.1 Storing System Texts

329

6.7.2 Translation-Friendly Message Texts

331

6.7.3 Text Environment

333

6.7.4 Character Set of Source Code

335

6.7.5 Splitting Texts

336

6.7.6 Codepages for Files

337

Appendices

339

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 Data Storage

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

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