Delphi is an object-oriented, visual programming language derived from Pascal. It is used to build desktop, mobile, web, and console applications, and is known for its rapid application development capabilities.
Delphi Anti-Patterns Overview
Delphi, despite being a powerful language for rapid application development, has several common anti-patterns that can lead to maintainability problems, performance issues, and bugs. Here are the most important anti-patterns to avoid when writing Delphi code.
Using String Concatenation in Loops
Avoid using string concatenation in loops. In Delphi, strings are immutable, so each concatenation creates a new string object, which is inefficient. Use TStringBuilder
(in newer Delphi versions) or TStringList
instead for better performance.
Not Using Try-Finally for Resource Management
Always use try-finally blocks when working with resources that need explicit cleanup, such as file handles, database connections, or objects created with Create
. This ensures resources are properly released even if an exception occurs.
Using Global Variables
Avoid using global variables. They create hidden dependencies, make testing difficult, and can lead to unexpected behavior, especially in multithreaded applications. Instead, pass dependencies explicitly through parameters or use design patterns like Singleton when appropriate.
Not Using Properties
Use properties instead of public fields. Properties allow you to encapsulate implementation details, add validation logic, and change the internal representation without affecting client code.
Not Using Interfaces for Decoupling
Use interfaces to decouple components. This makes your code more flexible, testable, and maintainable. Interfaces allow you to swap implementations without changing client code, which is especially useful for testing and dependency injection.
Excessive Form Coupling
Avoid excessive coupling between forms. Don’t directly access components on other forms; instead, provide public methods or properties that encapsulate the functionality you need. This makes your forms more maintainable and reusable.
Not Using Exceptions Properly
Use exceptions properly. Don’t swallow exceptions without handling them, and catch only the exceptions you can actually handle. Create custom exception classes for specific error conditions, and include meaningful error messages.
Not Using Generics
Use generics for type-safe collections and algorithms. Generics reduce code duplication and provide compile-time type checking, making your code more robust and maintainable.
Not Using Anonymous Methods
Use anonymous methods (closures) for callbacks and event handlers. They make your code more concise and can capture variables from the surrounding scope, which is useful for implementing callbacks without creating separate classes.
Not Using ARC/Automatic Memory Management
Take advantage of Automatic Reference Counting (ARC) on mobile platforms or use interface references on non-ARC platforms to simplify memory management. This reduces the risk of memory leaks and makes your code more robust.
Not Using RTTI and Attributes
Use Run-Time Type Information (RTTI) and attributes for tasks like serialization, validation, and mapping. This makes your code more declarative and reduces boilerplate code.
Not Using Unit Testing
Write unit tests for your code. Unit tests help catch bugs early, document expected behavior, and make it safer to refactor code. Use testing frameworks like DUnitX or DUnit to structure and run your tests.