The monkey patch is actually just a symptom of a more general paradigm in ruby. Metaprogramming especially comes in handy when handling methods that are similar except for identifiers. You can utilize define_method to create methods and when identifiers are added in the later phase the methods will be present beforehand. When you create a class by using the class keyword, you aren’t just deciding how future objects will behave. In the above Spin up your own blazing fast WordPress server in minutes with SpinupWP example, the method is utilized to invoke the “eats” instance method of the Birds class.
Only use metaprogramming if it provides a clear advantage. It consists of a series of objects that can pass messages back and forth among themselves. Drone Software Solutions: Build Powerful Drone Applications This message passing is generally what we refer to when we say “call a method.” Let’s take a look at the downcase method of String objects.
Pitfalls of using metaprogramming in Ruby on Rails application
It’s defined on the paperclip.rb and utilizes metaprogramming to define methods on the model. This is known as monkey patching, and it can become problematic if you redefine methods unintentionally. However, if everything goes as planned, it has the potential to significantly improve the program’s efficiency and performance.
They get transformed into byte-code or CIL (C#), or plain machine-code . You can’t modify these representations once the program has been compiled. What a gem.Metaprogramming is writing programs that write programs. For example, when a User model is defined in Rails with email as an attribute, a method called find_by_email will be generated. Ruby metaprogramming, one of the most interesting aspects of Ruby, enables the programming language to achieve an extreme level of expressiveness.
The block form of class_eval is preferable to the string-interpolated form. So we can see that this is the method that prints to STDOUT. Method, we see that this is not quite the same code as we had. Instead of opening up the class using the class keyword we use a class_eval. Our platform focuses on making the remote hiring process easier by providing top quality vetted developers from around the world.
When To Choose Ruby Metaprogramming
The Class constructor and the define_method allows you to generate classes and methods on the fly, as the program is running. At the top level, self is main, which is an Object. As soon as a Ruby program starts, the Ruby interpreter creates an object called main and all subsequent code is executed in the context of this object. This may not seem like much, but this is one of the constructs or ideas in Ruby that allows us to write very dynamic code, code that may not even exist when you write it. In the following section, we will look at how we can generate new code dynamically in Ruby using the define_method method.
It has tight coupling with other codes but is hidden and not apparent in some cases. As usual, developers even do not expect that there is such coupling at all. How to Use Enums in Rails Active Record Suppose you’re making a book tracking app to keep a log of all the books you consume.
Moreover because of the DRY principle metaprogramming avoids repeating the same codebases to remove code redundancy. When we use the send method, the name of the method and arguments are sent as a message to the calling object. Here we have opened a string and added a new method log on it, so you can understand how to open any class and add any method. This is where we answer your question; we explain the concept of Ruby metaprogramming, why and when to use it, its best practices, and real-world examples in this article.
Ruby metaprogramming is indeed intimidating, but mostRuby on Rails developershaven’t come across its real-world examples. This is where we enlist some of them, so take a look at it for a better understanding of metaprogramming in the real world. It might be difficult to understand this concept at first. Simply imagine the metaclass as a “personal assistant” of an object. This “personal assistant” helps an object to carry all the methods.
By defining a block like this, we are setting self to Developer’s metaclass for the duration of the block. As a result, the backend method is added to Developer’s metaclass, rather than the class itself. Now, in order to avoid writing more methods, we have two options — we can either use define_method or method_missing. Let’s What is Full Stack Developer now benchmark this using define_methodand method_missing. You are required to hire more experienced developers who will be aware of metaprogramming’s risks and could spot related problems faster. Metaprogramming allows us to add new code quickly, but it will add extra problems like support dependencies and understanding.
The list of HTTP verbs is stable — they almost never change. But by using metaprogramming, you have increased the complexity by dynamically defining methods for the HTTP verbs. We don’t have an explosion of methods problem here, so there is no need for any metaprogramming.
When you start, strive to make your code correct in the general cases, and simple enough that you can add more special cases later. Make this new class the class of the animal object. As soon as you call a method on another object, that other object becomes self. The ancestor chain is the path of classes from a class to its superclass, until you reach the root, i.e. The receiver is the object that you call a method on, e.g. in the statement myObj.perform(), myObj is the receiver.
- The connotation of “meta” is derived from Greek in which it simply means “beyond”.
- Eval method allows us to pass in a Proc object instead of a Binding object as the second argument.
- As a result, the backend method is added to Developer’s metaclass, rather than the class itself.
- The dependency should be in one direction, and should always point toward the stable abstractions.
- However, if everything goes as planned, it has the potential to significantly improve the program’s efficiency and performance.
- Metaprogramming in Ruby enables you to produce elegant, clean, and beautiful programs as well as unreadable, complex code that’s not maintainable.
Ruby developers can define an attached file on a model with the has_attached_file method. Sinatra is a Ruby gem or code library which extends the core functionality of Ruby. It handles the tedious task of mapping web requests to blocks of the Ruby code. To understand Ruby metaprogramming in an easy-to-understand style, read the Ruby metaprogramming book by Paolo Parotta. A benefit of class_eval is that it will fail if the class doesn’t already exist.
Defining Classes and Methods Dynamically
First we will add a new method to the Module class called delegar . When we invoke or call this method using the dot-notation, what we are really saying is that we are passing a message to the String, and it decides how to respond to that message. In this case, it responds with a downcased version of itself. How do you create an organization that is nimble, flexible and takes a fresh view of team structure?
Ruby Metaprogramming Real-World Examples
Metaprogramming is a technique by which you can write code that writes code by itself dynamically at runtime. This means you can define methods and classes during runtime. In a nutshell, using metaprogramming you can reopen and modify classes, catch methods that don’t exist and create them on the fly, create code that is DRY by avoiding repetitions, and more. In Ruby the term metaprogramming refers to the dynamic nature of the language, which allows you to define and redefine methods and classes at runtime.
Class methods are widely used while singleton methods not so much, but both types of methods are added to a metaclass of that object. One important thing to understand here is the meaning of self. The frontend method is a regular method that is available on instances of class Developer, but why is backend method a class method?