Bloomberg 1© 2024 Bloomberg Finance L.P. All rights reserved. Dependency Injection in C++: A Practical Guide CppCon 2024 September 18, 2024 Pete Muldoon Senior Engineering LeadBloomberg 4 Questions able to use it8 Bloomberg Where will we be going ? • Talk will be about inserting meaningful Dependency Injection in applications • Using various DI methods to achieve functionality swapping / instrumentation Production Code (or just giving up) • Talk is rooted in a real-world system not theory9 Bloomberg Dependency Injection : 1. Decreases coupling between functionality blocks 2. Used to make a class/function

1October 3, 2023 2 Libraries: A First Step Toward Standard C++ Dependency Management Bret Brown, C++ Infrastructure Lead, Bloomberg Bill Hoffman, CTO, KitwareHello! Welcome! Bret Brown C++ Infrastructure Projects as portable as the code they contain! ● ✓ Projects should be “cattle,” not “pets”! 7Why dependency management? 8Consensus: Managing dependencies == way too hard Q: Which of these do you find frustrating What’s a dependency bug? Missing interfaces: fangorn.cxx:2:10: fatal error: jsonlog/core.hxx: No such file or directory 10 This could be caused by other root problems!Pain: What’s a dependency bug

CONTENTS 1 Conan Documentation, Release 2.5.0 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by``mylib_b`` in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.4.1 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by``mylib_b`` in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.10.1 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by mylib_b in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.9.3 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by mylib_b in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.8.1 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by mylib_b in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.7.1 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by mylib_b in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.6.0 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by``mylib_b`` in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining

CONTENTS 1 Conan Documentation, Release 2.3.2 2 CONTENTS CHAPTER ONE INTRODUCTION Conan is a dependency and package manager for C and C++ languages. It is free and open-source, works in all platforms that will generate a new myapp package_id, for every change in the mylib recipe or binary. While a dependency between a static library mylib_a that is used by``mylib_b`` in general does not imply that a change also be created from a dependency graph resulting from a conan create or conan install com- mand, so it is possible to upload to a server all packages that belong to a given dependency graph just chaining