D is a general-purpose programming language with static typing, systems-level access, and C-like syntax. It combines the performance and safety of compiled languages with the expressive power and convenience of modern languages.
D Anti-Patterns Overview
D, despite being a powerful and versatile language, has several common anti-patterns that can lead to performance issues, maintainability problems, and bugs. Here are the most important anti-patterns to avoid when writing D code.
Excessive Use of Runtime Type Information (RTTI)
Avoid excessive use of runtime type information (RTTI) with cast
operations. This approach is slow, error-prone, and leads to brittle code. Instead, use polymorphism, interfaces, or templates to handle different types in a more type-safe and efficient manner.
Not Using @safe, @trusted, and @system Properly
Use D’s safety attributes (@safe
, @trusted
, and @system
) to clearly indicate the safety level of your code. Mark unsafe code as @system
, wrap it with carefully reviewed @trusted
functions, and aim to make most of your codebase @safe
. This helps prevent memory safety issues and makes your code more robust.
Excessive Use of Shared Mutable State
Not Using UFCS (Uniform Function Call Syntax)
Embrace Uniform Function Call Syntax (UFCS), which allows free functions to be called using method syntax. This makes your code more readable, especially when chaining operations, and helps create a more consistent API style.
Not Using Range-Based Algorithms
Use D’s powerful range-based algorithms from std.algorithm
and related modules instead of manual iteration and transformation. Range-based algorithms are more expressive, less error-prone, and often more efficient than manual loops.
Excessive Use of Dynamic Arrays
Be mindful of excessive use of dynamic arrays, which allocate on the garbage-collected heap. For small, fixed-size arrays, use stack arrays. For large arrays or performance-critical code, consider using custom allocators from std.experimental.allocator
to have more control over memory management.
Not Using Contract Programming
Use D’s contract programming features (in
and out
blocks) to specify preconditions and postconditions for functions. Contracts make your code more robust by clearly documenting and enforcing expectations about inputs and outputs.
Not Using Proper Error Handling
Implement proper error handling in your code. D uses exceptions for error handling, but you should consider using return values or std.typecons
types like Nullable
or Tuple
to represent success/failure states when appropriate, especially for operations that might reasonably fail.
Not Using Templates Effectively
Use templates effectively to create generic code that works with multiple types. Add constraints using static if and template constraints to ensure type safety and provide clear error messages when templates are misused.
Not Using Proper Memory Management
Implement proper memory management, especially when using manual memory allocation. Use destructors, the scope
statement, or RAII (Resource Acquisition Is Initialization) patterns to ensure resources are properly cleaned up.
Not Using Immutability
Use immutability (const
, immutable
) to make your code more robust and easier to reason about. Mark function parameters as const
when they shouldn’t be modified, and use immutable
for data that should never change.
Not Using Proper Modules
Organize your code into proper modules instead of putting everything in one file. This improves maintainability, compilation times, and allows for better encapsulation of implementation details.
Not Using Proper Documentation
Use proper documentation comments for your code. D supports DDoc, a documentation generator that processes specially formatted comments to create documentation. Include information about parameters, return values, exceptions, and examples to make your code more accessible to others.
Not Using Unit Tests
Include unit tests in your code using D’s built-in unittest
blocks. Unit tests help ensure your code works correctly and continues to work as you make changes. They also serve as executable documentation showing how your code is intended to be used.
Not Using Properties
Use properties (getters and setters) instead of public fields for class and struct members that need validation or might change implementation in the future. Properties allow you to encapsulate the internal representation while providing a simple interface.
Not Using Proper Concurrency Patterns
Use proper concurrency patterns when writing multithreaded code. Prefer message passing using std.concurrency
over shared mutable state. When shared state is necessary, use proper synchronization mechanisms like atomic operations, mutexes, or reader-writer locks.