Last Words

Reflection and code generation are powerful tools, but they come with trade-offs. Use them when they solve real problems, not just because they’re interesting.

When to Use Each Approach

Use Reflection When:

• Types are truly unknown at compile time
• Building generic libraries (pre-Go 1.18)
• Processing struct tags or annotations
• Implementing serialization/deserialization

Use Code Generation When:

• You need maximum performance
• Types are known at build time
• Eliminating repetitive boilerplate
• Building type-safe APIs

Avoid Both When:

• Simple solutions exist
• Performance isn’t critical and generics work
• The complexity isn’t worth the benefit

Performance Reality Check

The numbers don’t lie:

• Reflection can be 100x slower for field access
• Method calls through reflection are 300x slower
• Generated code performs like hand-written code

For hot paths, choose code generation. For occasional use, reflection is fine.

The Hybrid Approach

Many successful Go libraries combine both techniques:

• Use reflection for discovery and validation
• Generate optimized code for performance-critical operations
• Fall back to reflection for edge cases

Go’s Evolution

Go 1.18 generics changed the game. Many problems that required reflection or code generation now have simpler solutions. Before reaching for metaprogramming, consider if generics solve your problem.

Final Advice

Rob Pike said it best: “Clear is better than clever.” Use these techniques when they genuinely improve your code, not just because you can.

The best metaprogramming is invisible to users of your API. They should get the benefits without knowing the complexity underneath.

Start simple. Add complexity only when you have a clear need and understand the trade-offs.