Metaprogramming: What It Is and How It Works in Practice

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Celso Crivelaro
Celso Crivelaro
Head of Engineering

Table of Contents

Learn more about the aspects of metaprogramming, the different types, and the pros and cons here.
Published on
July 20, 2023
Updated on
April 11, 2024

There are a few jobs in the software world that we can call hidden gems, as not many people know much about them. Despite the growing popularity of the field, the roles of solutions engineers and metaprogramming professionals remain unknown to the general public.

Metaprogramming is a concept that has been around for a long time. It first gained popularity in the '70s and '80s when people used metaprogramming facilities alongside LISP programming languages to build and enhance artificial intelligence (AI) applications. Nevertheless, many companies are still new to metaprogramming and are unsure what it is and how it works.

What is Metaprogramming?

Metaprogramming remains unfamiliar to many business owners, team leaders, Agile teams, and even developers in the vast programming world. Yet, it can be found throughout many different programming languages, including JavaScript and Python, and can enhance several functions and features of these languages.

In simple terms, metaprogramming relates to the process of creating computer programs that will contribute to writing and manipulating other programs. This helps cut down time in writing source code, allows developers more flexibility, and frees up their time to focus on other tasks. But it’s also much more than that.

Metaprogramming allows applications to treat other applications as their data. As such, they can read, produce, examine, alter, and adjust other programs and even themselves while simultaneously running. They can also perform specific tasks, such as moving computations from run time to compile time. This allows programs to create methods upfront without defining them within the program.

Like with all programming languages, it’s essential to understand the basics of metaprogramming and the best practices in software development that can help improve the quality of applications, even through metaprogramming.

Programming Language Technique Basics

Metaprogramming can help operate other programs, but also itself. Introspection and reflection are two terms used in the metaprogramming world. Introspection is when a program uses metaprogramming to analyze and report on itself, whereas reflection is when it uses metaprogramming to apply modifications.

When a program uses metaprogramming to operate on other programs, it can write various functions, which include:

  • Assemblers
  • Compilers
  • Debuggers
  • Interpreters
  • Linkers
  • Loaders
  • Profilers
  • Metaprogramming circuit

On the other hand, metaprogramming can perform operations such as:

  • Finding out what file the program is in
  • Determining which function is currently running
  • Defining the thread that is currently running
  • Determining the class, properties, and constructed function of given objects
  • Seeing what classes are loaded and what their fields and methods are
  • Defining anonymous function and function arguments
  • Figuring out class definitions
  • Finding out the method body

Types of Metaprogramming

Examples of metaprogramming include template metaprogramming, C++ metaprogramming, and Elixir metaprogramming. A few other common types include Python, Ruby, and JavaScript, each with its functions and features.


Python is an object-oriented programming language, so everything written in Python is an object model. This includes functions, variables, and other components and classes.

Python metaprogramming consists of creating a metaclass from a class inherited through type. Metaclasses allow users to solve specific problems, such as code repetition and debugging. The only way metaprogramming gets supported in Python is through metaclasses.

Metaclasses are an object-oriented concept and are behind almost all Python code. However, many Python developers are unaware of what metaprogramming is and how it influences metaclasses. Those who want to be proficient in Python code should take the time to learn about metaclasses and the ways to use them.


Ruby metaprogramming has become accessible to developers of all skill levels, as there are plenty of resources, guides, and tutorials to help developers step into the world of Ruby metaprogramming. It allows developers to write programs that treat other programs as their data.

Developers can ask code questions, send messages, generate new methods, and more through metaprogramming Ruby. Some common questions that programmers find themselves asking their code include:

  • Am I able to respond to this method call?
  • What does my object ancestry chain look like?
  • What instance variables and methods have been defined?
  • What are the regular expressions being used?

Metaprogramming Ruby can help developers write repetitive code and analyze and debug what lines of code are doing in real-time. However, while metaprogramming in Ruby can be valuable, developers should use it carefully.


Developers often refer to metaprogramming as a magic technique in JavaScript, usually implemented through proxies. Proxies are a method in which objects can be wrapped and intercepted in custom behaviors. Proxies must have three elements:

  • Handler: A placeholder object consisting of traps is where the transition and conversion begin. It has operations and commands that JavaScript uses when operating on a target. The handler also defines and redefines intercepted operations.
  • Target: A target is an object created to be virtualized by the proxy. It is why the proxy gets created.
  • Trap: Traps are nested within handlers. They handle property access and communicate between targets.

Metaprogramming works with proxies to modify how specific code works. Modification can occur in various ways but must be within the bounds of expectations from typical codes. Developers can use metaprogramming with the help of online web scraping tools or their automated platform.

To implement metaprogramming with proxies, developers must consider the following:

  • Reflection
  • Forwards intercepted operations
  • Modifying through mutation
  • Creating proxy databases
  • An extra layer of security
  • Use of revocable proxies

Pros of Metaprogramming

There are many advantages when it comes to metaprogramming. The biggest one is that metaprogramming allows programs to write themselves. Since metaprogramming generates its code, there’s less room for error.

Automated code can save programmers time as they don't need to worry about writing complicated schemas. In addition to saving programmers valuable time, metaprogramming supports a faster market turnaround for application releases.

Other advantages of metaprogramming include the following:

  • Architecture stability equals time-saving opportunities
  • Code generation adds to any workflow
  • Reduced code repetition
  • Immutable metaprogramming
  • Improved code readability
  • Can help with boilerplate code

Cons of Metaprogramming

Users should, nevertheless, be aware of some drawbacks involved with metaprogramming. A significant disadvantage to many who want to step into the world of metaprogramming is syntax. Since metaprogramming primarily creates programs that write other programs, the syntax can be quite complicated, and the learning curve for metaprogramming can be steep. Many developers may feel discouraged when beginning their metaprogramming journey.

Because of the steep learning curve, metaprogramming can fall victim to incorrect use. This can result in unexpected errors, which can be difficult for the average developer to handle and cause vulnerability and risks within the system. Some of the most common errors occurring within metaprogramming include compilers being unable to recognize missing configuration constraints and invalid data resulting in unidentified exceptions.

Other disadvantages to metaprogramming include the following:

  • Metaprogramming doesn’t benefit all applications
  • Generating code through metaprogramming can be inflexible
  • Metaprogramming requires significant testing for compatibility issues
  • Compilation takes longer

How Does Metaprogramming Work in Practice?

Metaprogramming refers to a technique that allows code to get written during runtime. While there are many ways in which metaprogramming does this, here are the three main ones:

Runs a Wide Variety of Operations

Metaprogramming allows users to perform various operations simultaneously while the original program is still running. Typically, metaprogramming means that a programmer has written code that will continue to write itself or contribute to writing another program’s code.

Common operations include:

  • Code generation
  • Macros
  • Eval
  • Reflection
  • Introspection
  • Intercession
  • Modification

Creates Automatic Code Generation and Program Writing

Metaprogramming is known for its automatic code generation and program writing. There are several advantages to having code generated automatically. The most notable one is that it saves developers a lot of time in handwriting code. But how does automatic code generation work?

Automatic code gets generated through a uniform coding style. It generally looks at one application programming interface (API) development environment to create a similar one. Programs can typically evaluate their own and other program data, analyze it, and then manipulate the code into other domain-specific languages.

We should highlight that metaprogramming is supported only by programs that can alter themselves while running. So, for example, JavaScript programs can change behaviors during runtime, which means JavaScript supports metaprogramming.

Blends Methods Into Existing Projects

Metaprogramming can take methods from one program and blend them into existing projects. This allows developers to add methods to existing projects without creating or modifying a new method.

Blending methods from one project to another helps developers save time and resources.

Metaprogramming Implementation Easily

Metaprogramming is a highly beneficial method, but it can be challenging to implement, which is why businesses should hire the most experienced and skilled developers for the job. If you want to cut through the noise and find the best tech talent to support your metaprogramming efforts, Revelo got you covered.

Whether you want to implement metaprogramming into your business structure or build a mobile app with web3, Revelo can help. We are a talent marketplace striving to introduce businesses and entrepreneurs to Latin America’s best tech talent. In our vast talent base, you are sure to discover top-notch experts for numerous jobs, including the metaprogramming one.

Contact us to discover more about how Revelo works and start using metaprogramming to your advantage.

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