Okay, here's the summary of the provided transcript, formatted as requested:
Modern C++ Design: Beyond Silver Bullets
0:00 Introduction: The speaker, Claus, introduces the topic of "silver bullets" in software design, focusing on C++ with a simple shapes example.
0:00-0:50 Initial Problem: A shape drawing application needs to handle circles and squares initially but must be extensible for more shapes, in a large-scale project, not a small one.
1:47 Gang of Four Style: The first solution is using a traditional approach with a Shape base class, virtual functions, and a strategy pattern for drawing. Circle and Square inherit the base class and take a drawing strategy for rendering.
3:51 Factory Pattern & Abstraction: A ShapeFactory creates Shape objects from an external file. A drawShapes function iterates a vector of Shape pointers and draws them. The code is divided into abstract, high-level code and concrete, low-level implementations with a line of separation.
6:00 Code Extension: Adding a rectangle is simple, showcasing extensibility.
6:59 Modern C++: The example incorporates "modern C++" features (smart pointers, move semantics, auto, range-based for loops, string_view).
7:59 Skepticism: Audience is skeptical, recognizing that the solution isn't truly "modern" but rather using features in an old way of designing systems.
8:39 Gang of Four Criticism: This design style is compared to the "Gang of Four" patterns, which are considered outdated by some.
9:10 The Problem: The speaker claims most projects use this style, but there's a push for new approaches. Several C++ figures, including Johan Parents, Phil Nash, and John Kulp, are mentioned as critics of the traditional OOP approach.
11:15 Inheritance is the Base Class of Evil: This quote is referenced, indicating a move away from traditional OOP practices.
12:30 Review Feedback: The speaker shares a review of a prior talk, criticizing traditional OOP and advocating for templates and variants, showcasing that many see traditional OOP as outdated.
13:09 Variant-Based Solution: The speaker introduces a solution using std::variant to represent shapes (circle, square, rectangle, etc.).
13:23 Simpler Structures: The Circle and Square classes become basic geometric primitives without inheritance or virtual functions, with less code, no pointers and no explicit lifetime management.
14:18 Variant Abstraction: A Shape type is a std::variant holding different shape types. A shapes is vector<Shape>.
14:59 Factory without unique pointers:ShapeFactory creates shapes and directly puts them into the std::vector of shapes.
15:37 Abstraction for Factories: Introduced a variant to abstract the different types of factories
15:50 Open GL Drawer: An OpenGLDrawer class encapsulates drawing details, again, without base classes or virtual functions.
16:10 Drawer Abstraction: A Drawer type is a std::variant holding different drawing types.
16:23 Multi-Dispatch:drawShapes function takes two variants and uses std::visit, essentially achieving multi-dispatch.
17:15 Modern C++ Results: This variant based modern C++ code has no inheritance, no pointers, just values, is encapsulated and is simpler to write.
17:58 Simple vs Unfamiliar: The speaker notes that the approach might be unfamiliar, but it's actually simpler.
18:08 Performance Comparison: A performance test is done and it reveals the variant approach is faster than the traditional approach. It was not the point, but it is faster.
18:33 "One Feature to Rule Them All": A humorous take on how variant is praised by some people, referencing Phil Nash and Kenny Henny as advocates of functional programming in C++.
22:29 Architectural Boundaries: The speaker redraws an architectural boundary between "my code" and "your code" for the variant based implementation, showing how open gel drawer code is now your code because he is decoupled from OpenGL.
23:51 Coupling Concerns: However, issues with excessive coupling within the variant-based design are pointed out, as the high-level code still knows the concrete types.
25:27 Template Solution: Template functions are proposed for drawShapes and createAndDrawShapes to achieve inversion of dependencies, meaning that he would no longer care about what kind of shape variant you provide.
26:50 Template Limitations: The speaker acknowledges this might not solve all problems, especially for large codebases with many templates and potential long compile times.
28:00 Two Sides of the Design Spectrum:std::variant (functional) and virtual functions (OOP) are presented as opposite ends of the design spectrum, with different characteristics regarding type sets and operation sets.
28:39 Architectural Properties: Emphasizes that architectural properties matter and should inform design decisions.
30:29 Design Focus: The speaker notes a tendency to focus on C++ features over architectural concerns.
31:40 Conference Talk Statistics: Out of 48 talks at the conference, only six were about software design.
32:12 Conscious Decisions: When using a particular pattern or feature, one should be aware of the pros and cons and document the architectural decisions.
33:09 Modern is not Enough: Introduces the concept of "Progressive C++" as a way to break free from traditional OOP thinking and move beyond the term 'modern'.
34:28 Progressive C++: Defines Progressive C++ as abandoning standard C++ tradition with classes in favor of generic, functional, or value-based object-oriented coding practices.
36:32 Progressive C++ Design: The speaker moves on to a value based object-oriented approach for the shapes example.
36:38 Shape Concept & Model: A shape_concept and shape_model are introduced as building blocks for value based OOP design. Shape model will handle the drawing logic.
38:31 Decoupling: The base classes are removed from the Shape class. It's now a simple data class.
39:06 Type Erasure: The Shape class is introduced as an encapsulation for the shape model and is a type erasure mechanism for the polymorphic shape.
40:30 Templated Constructor: The constructor in Shape accepts a shape and a drawer and manages the instantiation.
41:08 Draw Function: The draw function uses a virtual dispatch to draw the shape. The class uses the copy rule of 5.
41:43 Value Semantics: The speaker makes it clear that Shape is meant to be a value.
42:20 Type Erasure: The implementation is called "type erasure" because it hides the underlying concrete type of a shape. The user only sees a value class.
42:41 Potential Optimizations: The user no longer has to manage memory, which allows for potential optimizations such as SBO.
43:16 Code Comparison: The code example is re-implemented with this technique and becomes less verbose.
44:58 No Allocation: The example is rewritten to not allocate anymore.
45:34 "My Code" and "Your Code" Separation: The separation between the two code bases is achieved. A rectangle can be introduced in "your code" without affecting the rest of the application.
47:08 Virtual Functions Are Hidden: The virtual functions are now encapsulated within the Shape class, and hidden from the user.
47:17 Performance Results: A performance comparison is conducted. This approach is not faster by much, but when taking into consideration optimizations such as SBO, there is potential to perform better.
49:10 When to Use OOP vs Functional: The speaker explains when to use the functional std::variant or the OOP-like type_erasure implementation. Variant is better at lower levels, type erasure is better at higher levels.
50:50 Two Sides of the Same Coin: These two approaches should be seen as "two sides of the same coin" instead of replacements for one another.
51:26 Prioritize Architecture: The speaker emphasizes considering architectural properties first, before picking a specific solution.
51:48 Reflection: The speaker suggests that C++26's reflection feature may enable the generation of type erasure wrappers automatically, but also warns against seeing reflection as a "silver bullet".
52:50 Rule for Software Design: Consider advantages and disadvantages of all solutions.
53:33 Summary: No silver bullet; several solutions must be known, and decisions must be based on an understanding of the problem.
54:16 Q&A: The speaker answers questions regarding libraries, Microsoft's proxy, and Boost type erasure. He recommends writing your own type erasure implementation if you need this abstraction, for now, or wait for reflection. Also he dismisses CRTP as a general solution for inheritance.
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