Explore the concept of Dependency Injection in C++ through this comprehensive conference talk from C++Now 2024. Delve into the fundamental building blocks of Dependency Injection, including link-time substitution, null-valued objects, interfaces via inheritance, templates, smart pointers, and polymorphic function wrappers. Examine the strengths, weaknesses, and ideal problem spaces for each approach. Learn effective strategies for implementing Dependency Injection, avoiding pitfalls like singletons and global state, and introducing the concept into legacy codebases. Gain insights on injecting multiple dependencies into classes and functions without major code overhauls. By the end of the talk, develop a coherent strategy for incorporating Dependency Injection into your C++ applications, enhancing code testability, extensibility, and flexibility.