How to Improve Code Quality: Delphi

Delphi is a Rapid Application Development system that uses Object Pascal. As Object Pascal is relatively unfamiliar to most, you need to know how to improve code quality when writing Delphi code.

Delphi is not just a programming language. It's an entire IDE that supports rapid application development. It is mainly used for the creation of Windows desktop applications, but it supports cross-platform development for macOS, Linux, iOS, and Android.

What is the Current Status of the Delphi Programming Language? 

Some people think Delphi is legacy or not relevant anymore, but this is not true. It’s still one of the major programming languages with an active developer community. Currently, it is managed by a company called Embarcadero. They have consistently released updates and new versions. For example, Delphi 12 Athens was released on September 9, 2023. This version introduced several enhancements, such as

• Improved High DPI Support – Better scaling and rendering for modern high-resolution displays.
• Optimized Compiler Performance – Faster compilation times and improved code execution for better efficiency.

Next, Delphi 12 Athens - Release 2 was released on September 12, 2024, as Update 2.

These kinds of releases prove how well Delphi is still managed for active development by introducing features suitable for modern-day development.

What is the Current Popularity of Delphi?

Delphi has seen a steady rise in popularity in recent years. The TIOBE Index as of February 2025 ranks it 9th with a 2.18% rating. It was in 12th place the year before. This upward trend shows that interest in the language is growing.

Delphi also has a stable presence among developers. In Stack Overflow’s 2023 developer survey, 3.23% of respondents reported using Delphi. This number has stayed almost the same as the previous year.

Other rankings show similar growth. Its current rating in the TIOBE Index is higher than PHP and Rust. This proves Delphi is still relevant in the programming world.

Why Code Quality is Important for Delphi

Delphi’s code style is a bit different from other high-level languages like Java and JavaScript. Therefore, maintaining good code quality is essential when programming in Delphi. Here are several reasons why code quality is important for Delphi.

• Delphi doesn’t have automatic garbage collection like Java or Python. It requires explicit memory management. Poorly managed code can lead to memory leaks.
• Delphi heavily relies on event-based programming and visual components. Poorly written event handlers or tightly coupled components can make applications difficult to debug, extend, or modify. 
• Delphi’s strong typing system reduces runtime errors but requires careful attention to data types. Poorly structured code may lead to unnecessary type conversions or hidden bugs that are harder to catch at runtime.
• Delphi compiles directly to native machine code, This means there are fewer runtime safety mechanisms compared to languages like C# or Java. Bad practices such as improper exception handling or unsafe pointer usage can lead to crashes.
• Delphi is widely used in enterprise applications. Many of these applications have been in production for decades. Therefore, maintainability is a major concern for Delphi code language. This reduces technical debt and eventually makes it easier for developers to update or refactor legacy systems.
• Delphi produces highly optimized native applications for Windows, macOS, iOS, and Android. Poorly written code can lead to unnecessary memory consumption, slow execution, or inefficient GUI rendering. 
• Many Delphi applications are used in industrial control systems, medical devices, and embedded environments. These systems demand high reliability, as failures could have serious consequences. High-quality code helps prevent crashes, memory leaks, and unexpected behaviors.
• Unlike some modern languages with massive ecosystems, Delphi has a smaller but dedicated developer base. Well-structured, readable code is essential for collaboration, especially when working in teams where new developers might need to take over existing projects. 

There are several factors that make a code high-quality. We can identify them as the five pillars of code quality. Let’s see what they are. 

How to improve code readability?

Code should be easy to understand, with clear variable names, consistent formatting, and proper indentation. Other developers should be able to understand its purpose quickly.

1. Use meaningful variable and function names.

Example:

Wrong practice : 

x := 1500;

Right practice: 

TotalSales := 1500;

2. Follow Pascal casing and indentation conventions.

Example:

Wrong practice:

 procedure calcprice;

begin

result:=baseprice*1.2;

end;

Right practice:

procedure CalculatePrice;

begin

  Result := BasePrice * 1.2;

end;

3. Break large functions into smaller, reusable procedures.

4. Comment why the code exists, not just what it does.

Example:

// Adjust price based on sales tax rate for different states

Price := BasePrice * SalesTaxMultiplier;

How to improve code maintainability

Delphi projects often require long-term maintenance. Well-structured code reduces technical debt. Knowing how to improve code maintainability is important for the code to be efficient and easier to manage over time.

1. Follow the Don’t Repeat Yourself principle.

Example:

Wrong practice: Using repetitive code

function CalculateTaxA(Price: Double): Double;

begin

  Result := Price * 0.05;

end;

function CalculateTaxB(Price: Double): Double;

begin

  Result := Price * 0.05;

End;

Correct practice: Using Reusable code

function CalculateTax(Price, TaxRate: Double): Double;

begin

  Result := Price * TaxRate;

end;

2. Remove dead code.

3. Use modular programming with classes and units.

4. Version control with Git for tracking changes.

How to improve code efficiency

Well-written code minimizes unnecessary computations, memory usage, and execution time. Optimized algorithms and data structures improve application performance and show how to improve code efficiency. Delphi compiles directly to native machine code. This means developers must write efficient logic to avoid slow performance, memory leaks, and excessive CPU usage.

1. Optimize loops and database queries.

Example:

for I := 0 to Length(DataArray) - 1 do

  if DataArray[I] = TargetValue then

    ShowMessage('Found!');

Correct practice: Use Find where applicable

if DataList.IndexOf(TargetValue) <> -1 then

  ShowMessage('Found!');

2. Avoid unnecessary object creation and destruction.

Example:

for I := 0 to 1000 do

begin

  TempObj := TSomeClass.Create;

  try

    // Processing

  finally

    TempObj.Free;

  end;

End;

3. Reuse objects whenever possible.

4. Profile applications using Delphi’s built-in tools - Identify slow code and memory leaks before deployment.

5. Use threads carefully for parallel execution - Avoid freezing the UI in event-driven applications.

How to improve code Reliability

Delphi applications power large businesses, where stability is a must. Delphi Praxis focuses on writing reliable code to prevent unexpected crashes and incorrect outputs. 

1. Use structured exception handling.

Example:

Wrong practice: No error handling

Query.Open;

Correct practice: Handle potential failures

try

  Query.Open;

except

  on E: Exception do

    ShowMessage('Error opening query: ' + E.Message);

end;

Validate user input to prevent incorrect data processing

if TryStrToInt(UserInput, ParsedValue) then

  ProcessValue(ParsedValue)

else

  ShowMessage('Invalid input. Please enter a number.');

2. Use logging for debugging and diagnostics - Integrate tools like CodeSite or simple log files for tracking issues in production.

3. Write unit tests using Delphi’s DUnitX framework - Test individual components before deployment.

How to improve code Security

Delphi applications often handle enterprise data, financial transactions, and industrial controls. Secure coding practices are essential to prevent attacks and data breaches. One of the most effective methods for preventing SQL injection is by using parameterized queries. Below is a Delphi database example code demonstrating the correct approach for handling user input securely.

1. Prevent SQL injection by using parameterized queries.

Example:

Wrong practice: Unsafe SQL query

Query.SQL.Text := 'SELECT * FROM Users WHERE Name = ''' + UserInput + '''';

Query.Open;

Correct practice: Use parameters

Query.SQL.Text := 'SELECT * FROM Users WHERE Name = :Name';

Query.ParamByName('Name').AsString := UserInput;

Query.Open;

2. Encrypt sensitive data - Use Delphi’s AES encryption or Indy’s hashing functions.

3. Avoid hardcoding credentials in Delphi source code.

Example:

const API_KEY = 'YourSecretAPIKey'; 

4. Secure network communication - Use TLS/SSL for HTTP requests instead of plaintext connections.

5. Regularly update Delphi and third-party components - Security vulnerabilities in older libraries may expose applications to attacks.

How do you Measure Code Quality?

Measuring code quality involves evaluating various factors to make sure the code is efficient and secure, with each having several indicators.

Reliability

Reliability is measured by how consistently the code performs without errors or crashes.

• Exception Rate: Track exceptions/errors logged during runtime.
• Bug Density: Bugs identified per 1000 lines of code.
• Failure Rates: Frequency of application crashes or unexpected shutdowns.

Maintainability

Maintainability assesses how easily the code can be understood, how to debug Delphi code, and enhanced over time.

• Cyclomatic Complexity: Measures how complex the control flow is.
• Lines of Code per method/class: Shorter, modular methods are preferred.
• Code Duplication: Percentage of repeated code.

Performance and Efficiency

How effectively system resources are used by the code.

• Execution Time: Benchmark tests for performance-critical routines.
• Memory Usage: Profiling tools to identify and reduce memory footprint.
• Resource Leaks: Detection of memory leaks or unmanaged resources.

Security

Evaluates how resilient the code is against possible attacks.

• Security Vulnerability Count: Number of vulnerabilities identified by scanners.
• Vulnerability Reports: Reports from penetration testing, app security testing or static analysis.

Other Methods to Improve Code Quality for Productivity and Maintainability

There are other ways to improve code standards in Delphi development, some of which are discussed below.

1. Catch Problems Early with Static Analysis - Detection of probable issues during the early stages of development prevents delays and increases software stability. FixInsight is a static code analyzing tool for Delphi. It analyzes source code for bugs, errors, and code convention breaches. It detects problems before they become severe. This guarantees a smooth deployment cycle.
2. Save Time with Auto-Formatting of Code - Cleanly formatted code is more readable and easier to maintain. The DelForExp code formatter in the free Delphi utility GExperts helps developers format their code in a neat and organized manner. RAD Studio's built-in formatter also insists on consistent indentation and alignment. GExperts also offers an alignment helper, which aligns assignments in columns for better readability.
3. Manage Dependencies Without Scripting - Dependencies can lead to version conflicts and wasted time if manually handled. DelphiPI automatically installs components and manages package dependencies within the Delphi IDE. It simplifies the management of third-party libraries and internal modules by compiling, installing, and setting up source paths.
4. Easily Create Delphi Code Documentation - Cleanly documented code speeds up future development and debugging. DelphiCodeToDoc generates formatted documentation in JavaDoc-style format, which is more readable to understand the functionality and behavior of different modules. DelphiCodeToDoc helps teams code cleaner, well-referenced code by providing precise documentation from Delphi source files.
5. Access Databases with Clean Code Conventions - Proper database access is required for Delphi applications. MySQL Data Access Components provides direct native access to MySQL and MariaDB for Delphi, C++ Builder, and Lazarus development. MyDAC does not use the Borland Database Engine and dbExpress and provides a significantly faster and optimized way of using database connections.

Code Vulnerabilities in Delphi

Delphi applications, like any software, are exposed to security risks. Developers need to be aware of the most common vulnerabilities to build secure applications. In Delphi, five key vulnerabilities often appear.

• SQL Injection
• Cross-site Scripting
• Buffer Overflow
• Insecure Authentication
• Sensitive Data Exposure

Not all vulnerabilities are of the same threat level. There are four levels of severity.

• Critical  - Has a risk of exploitation and must be fixed immediately.
• High  - Can have a severe effect if exploited and will typically lead to data loss or system compromise.
• Medium  - Has a moderate risk that may get exploited under certain conditions.
• Low  - Has a minimal effect, not probable to be exploited but should be fixed anyway.

Early detection and patching of weaknesses reduce security risk. Below are some good ways to detect issues in Delphi programs.

• Use Static Analysis Tools – Automated tools like DerScanner, FixInsight, Pascal Analyzer, and SonarDelphi scan source code to detect probable security weaknesses and bad coding styles. These tools to improve code quality help catch errors early and easily.
• Conduct Manual Code Reviews – Review code regularly for unsafe use of memory, poor exception handling, and unsafe database queries to catch vulnerabilities not caught by automated tools. Also, understanding how to improve code review process can improve the effectiveness of manual reviews.
• Write Unit and Dynamic Tests – Running unit tests with DUnit or DUnitX can find logic errors. Dynamic testing can find security defects present only at runtime.

By applying these methods, Delphi developers can strengthen application security, reduce risks, and guarantee stable and secure software for users.

What is a Secure Code Review SCR?

A Secure Code Review is a systematic and thorough analysis of application source code to identify security vulnerabilities, weaknesses, and flaws before they reach production. It is performed either manually by security experts or automatically through specialized security tools. The goal of SCR is to detect and address vulnerabilities early so that security risks are reduced.

Why Do a Secure Code Review?

After performing SCRs, developers can enjoy the following benefits. 

• Discover and eliminate vulnerabilities early in the software development lifecycle.
• Improve software security by enforcing secure coding standards.
• Comply with industry regulations and standards.
• Reduce opportunities for cyberattacks, data breaches, and reputation damage.

How Secure Code Review Applies to Delphi Code Quality

SCR plays an important role in enhancing Delphi code source by identifying and addressing security vulnerabilities throughout the development process.

• Identifying Common Security Vulnerabilities -  SCR helps detect SQL injection, buffer overflows, and insecure memory management, which can be concerns in Delphi’s native applications. Since Delphi lacks built-in garbage collection, manual memory management flaws can introduce serious security risks
• Correct Exception Handling - Delphi application exceptions can leak confidential information or crash the application if not handled correctly. An empty catch block should be avoided, as it can silently swallow exceptions and lead to undetected issues in the application. SCR mandates structured exception handling to prevent exposing internal application data.
• Checking Hardcoded Credentials & Sensitive Data Exposure - SCR identifies hardcoded API keys, passwords, and encryption keys in Delphi source code. Delphi applications often use databases, network services, and local storage and therefore, must encrypt sensitive information securely.
• Checking Secure Coding Practices in Object Pascal - SCR guarantees type safety, proper object lifecycle management, and prevention of pointer-related vulnerabilities. Since Delphi compiles to native machine code, unsafe memory access and pointer misuse can lead to security exploits.
• Assessing Secure Networking and API Calls - SCR verifies the use of TLS/SSL for secure communication in Delphi’s Indy or REST components. It makes sure that Delphi applications follow OAuth or token-based authentication instead of passing credentials directly.

How DerScanner Helps Improve Delphi Code Quality

DerScanner unifies code quality analysis and security vulnerability detection into a single platform. With nearly 100 new rules for Delphi/Pascal, DerScanner helps developers write cleaner, more maintainable code, catch security flaws early, and learn how to improve quality of code throughout the development process.

Static Code Analysis for Delphi

DerScanner scans Delphi source code to detect potential errors, bad practices, and security risks. Unlike traditional static analysis tools, it integrates security and quality checks. Then, developers can fix logic errors, enforce best practices, and reduce technical debt before issues reach production. By providing real-time feedback and detailed reports, developers can maintain high coding standards without slowing down development.

Enforcing Delphi Best Practices

DerScanner incorporates Delphi/Pascal-specific coding standards to improve readability, maintainability, and performance. It makes it so that naming conventions follow standard practices, such as prefixing types with T, exceptions with E, and interfaces with I. It also helps organize class structures by maintaining the correct order of visibility sections, such as private,  protected, public and published. By enforcing structured formatting and guiding developers on how to improve code performance, DerScanner makes Delphi code easier to review, debug, and extend. This will, in turn, help developers code better in Delphi.

Improving Error Handling and Reducing Bugs

Many runtime errors occur due to improper exception handling and weak type conversions. DerScanner identifies places where developers should use TryStrToInt and TryStrToFloat instead of older, unsafe conversion methods. It also flags bad memory management practices and makes sure that objects are created and freed correctly to prevent memory leaks and crashes. This results in more reliable and efficient Delphi applications.

Avoiding Duplicated and Unstructured Code

Code that is not structured properly is difficult to manage and often leads to increased expenditure and errors. DerScanner applies the Don't Repeat Yourself principle to assist developers in removing unnecessary complexity through redundant code restructuring. It also resolves functions with overly convoluted or deeply nested logic so that they are easier to understand. DerScanner improves code maintainability over time by lessening perceptual complexity.

Integration with Delphi Development

Using DerScanner will eliminate all difficulties when integrating with Delphi workflows. Developers can scan code from their repositories, or alternatively perform a manual upload for analysis. The reports provide a detailed breakdown of issues found in the scan, such as the precise locations in the code, severity, and suggested resolutions. Also, DerScanner is working with Embarcadero to provide direct integration with RAD studio, which allows Delphi developers to resolve code quality issues without leaving the IDE.

How Does Software Composition Analysis Improve Delphi Code?

Derscanner is looking to provice Software Composition Analysis for Delphi applications. It is a security practice that helps identify and manage risks in third-party libraries and open-source code used in software applications.

Delphi applications often rely on third-party libraries such as VCL and FMX components. SCA helps find vulnerabilities in these dependencies. Developers can update or replace outdated or insecure components before they become a risk.

SCA also helps maintain compliance with licensing and security standards. This reduces legal and security concerns. Regular scans prevent vulnerabilities from building up over time and keep Delphi applications secure. To enhance Software Composition Analysis, continuous monitoring and updating of dependencies help keep the code secure against new threats.

What is Delphi Code Injection?

Delphi code injection is a code injection vulnerability where a Delphi application is altered to execute commands that were not intended by the developer. This takes place when inputs provided by users are not properly handled and allows for executable code to be injected into ShellExecute or WinExec function calls. 

Developers should strongly consider filtering and validating user supplied inputs prior to passing them in system defined procedures to avoid code injection. Instead of allowing shell commands to be dynamically constructed, other methods such as safer parameterized execution should be implemented. Functions like CreateProcess should be used with separate arguments rather than concatenated strings. Running the application with the least privilege and using secure coding practices significantly reduce the risk of exploitation.

DerScanner is a static analysis security tool designed to detect vulnerabilities in Delphi applications. It scans the source code for dangerous patterns, such as improper use of shell execution functions, and highlights potential security flaws. It also provides detailed reports and recommendations for fixing vulnerabilities.

What is ABAP Application Security?

ABAP stands for Advanced Business Application Programming. It is SAP’s primary programming language, specifically designed for developing applications in the SAP ecosystem. Modern enterprises rely heavily on SAP systems to handle sensitive business processes and data. Therefore, improving ABAP application security with Static Application Security Testing and Delphi static code analysis is very important.

Delphi developers can learn from ABAP application security practices, as both languages share common security concerns in application development.

Conclusion

Delphi is still a viable tool for developing applications on many platforms. While focusing on various key factors, developers can make their Delphi source code stable and secure. Executing best practices like modular programming, proper exception handling, and secure coding methodologies can minimize threats and improve the performance of applications. Through continuous updates and an active community, Delphi will remain a good language for programmers who want to develop stable and efficient programs.