Back to Basics Designing Classes (part 1 of 2) Klaus Iglberger, CppCon 2021 klaus.iglberger@gmx.de2 Klaus Iglberger C++ Trainer/Consultant Author of the C++ math library (Co-)Organizer Beck, TDD by Example)The Challenge of Class Design 10 Guideline: Design classes for easy change. Guideline: Design classes for easy extensions.Design Guidelines 11 Back to Basics: Class Design (Part ) const; 23 Using inheritance naively to solve our problem easily leads to … … many derived classes; … ridiculous class names; … deep inheritance hierarchies; … duplication between similar implementations

Back to Basics Designing Classes (part 1 of 2) Klaus Iglberger, CppCon 2021 klaus.iglberger@gmx.de2 Klaus Iglberger C++ Trainer/Consultant Author of the C++ math library (Co-)Organizer duplication to enable you to change everything in one place (the DRY principle). Guideline: Design classes for easy change.Data Member Initialization 24 struct Widget { Widget() : Widget(42) // Decisions 63 Guideline: Encapsulate design decisions (i.e. variation points). Guideline: Design classes for easy change.Qualified/Modified Member Data 64 Back to Basics: Class Design (Part 1) The Challenge

Consulting, Inc. www.stevedewhurst.com 1 Copyright © 2020 by Stephen C. Dewhurst and Daniel Saks C++ Classes  Only non-static data declarations in a class definition add anything to the size of class objects duration.  Therefore, we won’t be discussing static data members.  Type member (included nested classes) do not affect class layout.  Non-virtual member functions have no effect on class layout.  However Space…  An empty class has no non-static data members, no virtual functions, and no virtual base classes.  We often call these types/objects/closures “stateless.”  However, even an empty class must occupy

linked in with all of the real dependencies • One for Testing • Simple implementation of some Test classes / functions • Alternate implementation files(.cpp) live in an alternate/test code branch • One link Dependency Injection Dependency Injection roadblocks : • Objects full creation hidden inside functions/classes ❑ No handle to inject new functionality ❑ Default class constructors initialized via Singletons/GlobalsBloomberg functions/classes ❑ No handle to inject new functionality ❑ Default class constructors initialized via Singletons/Globals • Reaching through multiple objects ❑ Long chains of mock classes needed as

log_sink classes: classes:CASE STUDY: LOGGING CASE STUDY: LOGGING Given the Given the push push function, we can write various function, we can write various log_sink log_sink classes: classes: "ordinary" push push function, we can write various function, we can write various log_sink log_sink classes: classes: "ordinary" sinks that send entries to di�erent places (�le, output window, etc) a �lter sink push push function, we can write various function, we can write various log_sink log_sink classes: classes: "ordinary" sinks that send entries to di�erent places (�le, output window, etc) a �lter sink

觉，欣喜自己能在迷时找到良师。 武汉"wking" Microsoft Developer Studio 与MFC（Microsoft Foundation Classes）相配合，构成了一个强大 的利用C++ 进行32 位Windows 程序开发的工具，但是由于MFC 系统相当庞大，内 容繁杂，并且夹杂着大量令初学者莫明其妙的macros，更加大了学习上的难度。 框架编程？ 侯俊杰回复：的确如此。MFC 其实就是把Windows API 做了一层薄薄包装，包装于各个设 计良好的classes 而已。所以，掌握了MFC framework 架构组织之后，接下来在programming 实务方面，就是去了解并运用各个classes，而各个classes 的member functions 有许多就是 Windows APIs 的一对一化身。 xvii 左营luke@orchid Handling） / 096 Template / 100 Template Functions / 101 Template Classes / 104 Templates 的編譯與聯結 / 106 第３章 MFC 六大關鍵技術之模擬 / 109 MFC 類別階層 / 111

[FUTURE] AST INJECTION (META/REFLECTION)? [NEARER FUTURE?] TEMPLATES IN LOCAL CLASSES [NEARER FUTURE?] TEMPLATES IN LOCAL CLASSES 6 . 20WORKING AROUND LIMITATIONS WORKING AROUND LIMITATIONS PRECOMPILED HEADERS [NEARER FUTURE?] TEMPLATES IN LOCAL CLASSES [NEARER FUTURE?] TEMPLATES IN LOCAL CLASSES P1988 ALLOW TEMPLATES IN LOCAL CLASSES P1988 ALLOW TEMPLATES IN LOCAL CLASSES 6 . 20WORKING AROUND LIMITATIONS WORKING TEMPLATES IN LOCAL CLASSES [NEARER FUTURE?] TEMPLATES IN LOCAL CLASSES P1988 ALLOW TEMPLATES IN LOCAL CLASSES P1988 ALLOW TEMPLATES IN LOCAL CLASSES P2044 MEMBER TEMPLATES FOR LOCAL CLASSES P2044 MEMBER TEMPLATES

references can destroy instances of derived classes. ▪ protected and non-virtual: ▪ Base class pointers or references cannot destroy instances of derived classes. Destructors should not fail; make them organized concepts. Base classes typically act as interfaces. ▪ Interface inheritance uses public inheritance. It separates users from implementations to allow derived classes to be added and changed users of base classes. ▪ Implementation inheritance often uses private inheritance. Typically, the derived class provides its functionality by adapting functionality from base classes.Implementation

resources • No elaborate run-time support (e.g., no GC) • Manage complexity – based on Simula • Classes • Strong static type checking Stroustrup - C++ safety -CppCon - October 2023 15 I needed a tool C in 1979 aka “Classic C” double sqrt(); double x = sqrt(2); /* crash */ • C with classes in 1980 (C and C++ today) double sqrt(double); // argument type required double x = sqrt(2); conservativeKey idea: “Represent concepts in code” • Direct representation of ideas in code • Focus on classes • Make code more declarative • Make more information available to compilers • Early examples •

https://AndreasFertig.com post@AndreasFertig.com 3Training services ■ I’m available for inhouse classes, onsite or remote. ■ You can also book my course at the CppCon Academy. ■ Or one of my fellow instructors post@AndreasFertig.com 5A class ■ C++ adds classes for object-oriented programming. ■ The constructors B are called when the object is cre- ated. ■ Data fields of classes should be initialized in the constructor initialization list C . ■ The body of the constructor D is available for further opera- tions. ■ Classes can consist of member functions E and data fields G with different access rights A . ■ For everyone: