Make monkey patching in ruby less risky with refinements. Going with the most general of definitions, such as a way to extend or modify the runtime code of dynamic languages is problematic in ruby, because it would cover. Well cover topics such as inheritance and encapsulation and get at the core of what ruby programming is about. When we see an opportunity to move a util method to one of the existing rubys standard classes, thats when we open the existing ruby class and add that method there. A class is the blueprint from which individual objects are created. It can be very difficult to debug problems caused by monkey patching, and it can easily cause bugs when the patched class changes. Ruby is like a sharp knife, it can be extremely effective, but its usually your own fault if you cut yourself. Whats the deal with monkeypatching and why is everyone. Why rubys monkey patching is better than land mines. Hi, some of you might have noticed an article i published last week on why i currently feel lonely in the ruby community because i dont share a. You can take a class, any class, even a ruby standard library one, open it up and add other methods to it. When you monkey patch core classes, you add to the core ruby apis.
According to the creator, ruby was influenced by perl, smalltalk, eiffel. Covering class definition, instantiation, instance variables, accessor methods, class variables, class instance variables, class methods, class visibility. The practice of altering methods in rubys core classes. Monkey patching is the practice of adding methods to or altering ruby s core classes.
Starting off the list for examples of metaprogramming is monkey patching. To illustrate monkey patching well make some changes to the good old string core class. In ruby, python, and many other dynamic programming languages, the term monkey patch only refers to dynamic modifications of a class or module at runtime, motivated by the intent to patch existing thirdparty code as a workaround to a bug or feature which does not act as desired. Programming tutorial on instance variables and classes. Sep 28, 2016 in below text, well use term monkey patch for changing behavior of some ruby classes and modules you havent written, whether it be core classes, or standard library ones, or classes of thirdparty library, gem, framework. Public, private and protected, getter and setter methods. Jun 17, 2015 ruby is like a sharp knife, it can be extremely effective, but its usually your own fault if you cut yourself. These features have been discussed in the chapter object oriented ruby.
Feb 23, 20 monkey patching and if that isnt enough to make you run away screaming, monkey patching is a wonderful way of rewriting, at runtime, the behavior of a class, by simply replacing an existing class function with a new one. Even if the runtime already contains a monkeypatch with the backported functionality, we consider the method as dirty and activate the refinement for it. However i am not aware of an unbiased alternative to monkey patching. Refinements become most important any time youre making modifications to existing methods on core classes in ruby or any other widely used code base. If i patch it to make it behave like hashwithindifferentaccess it could break many librariesframeworks in unexpected ways. Ruby is a perfect object oriented programming language. In ruby, a monkey patch mp is any dynamic modification to a class and is often used as a synonym for dynamically modifying any class add new or overwrite existing methods at runtime. Php has some monkey patching capabilities out of the core, via the runkit extension but thats for userland classes and. If nothing happens, download github desktop and try again.
The ability to change the way classes behave at runtimeaka monkeypatching has been used by many libraries and frameworks to decorate rubys core classes with additions andor replacements. Monkey patching is the term used to describing extending a classs functionality as shown above, or overwrite existing methods. I also came across a lot of horror stories regarding the trials of debugging ruby sw because someone included a relatively harmless library to do a little job but which patched some heavily used core object without telling anyone. This is possible because ruby supports a concept known as open classes, which lets you do exactly this, i. Some im not so crazy about and its usually areas where they tried to copy perl. Every app with core patches feels a little bit different. In ruby, its possible to add methods to absolutely any class including string, integer and other core classes. It is a powerful technique that has become popular in the ruby community at least in part because the ruby language makes it so easy. Ruby makes it easy to extend its builtin classes, which can be very convenient and lead to more readable codebut it can also be dangerous.
Monkey patching is especially useful for modifying code from third party vendors. While some of it could be used as refinements, i suspect much of it will remain core extensions bc it represents rails dsl, so to speak. Yes, its a weird name, but its a powerful and dangerous tool. Classes and objects inheritance collaborator objects modules build an object oriented rps game coding tips crc cards rps bonus features working with objects in ruby. Is there a purely technical term for monkey patching. Getting a stronger ruby community with a different mindset. Ruby is a dynamic, thoroughly object oriented programming language with a focus on developer happiness and productivity. In objectoriented programming, a class is an extensible programcodetemplate for creating objects, providing initial values for state and implementations of behavior. Before answering the question lets understand what monkey patching is. Specifically, the goal is to make it possible to extend core classes, but to limit the effect of those extensions to a particular area of code. The features of the objectoriented programming language include.
I see open classes not as an alternative name, but as a prerequisite for monkey patching. In ruby land, monkey patching is the act of modifying the methods on someone elses class. In addition, ruby doesnt treat core classes any differently from userdefined classes, so this gives you a lot of power to completely change the behaviour ruby. The first thing you need to understand is that the purpose of refinements in ruby 2. Unlike some languages, a ruby class is never closed. Refinements are designed to reduce the impact of monkey patching on other users of the monkeypatched class. This practice, known as monkey patching, is common in the ruby world, and since ruby 2, its been possible to mitigate some of the risks using refinements.
It does so by creating a new class, a singleton class, from the objects original class. Is it doing something like the following, or is it something else. Monkey patching is the new black in the ruby community. Lets have a look at the whys and hows of this proposal the power of monkey patching. Ruby makes it easy to add, remove, and replace methods on any class even core classes like array but it is generally frowned upon.
This course is designed to give you everything you need to start developing software in ruby quickly. Jul 12, 2008 monkey patching is the new black in the ruby community. A common approach in ruby is to consider overriding existing methods to be monkey patching, but adding methods not to be, even though most non ruby definitions would include both. By the way, php has some monkey patching capabilities out of the core, via the runkit extension but thats for userland classes and functions. When you do it well, it makes your code feel more like ruby. Readme corefines is a collection of general purpose refinements for extending the core capabilities of rubys builtin classes. The practice of adding methods to or altering rubys core classes. One of the most useful among these specialities is that, in ruby, all classes are mutable. And i dont like the idea of monkey patching core classes either. This is called monkey patching or open classes in ruby. Rubys open classes are powerful but can easily be misused.
Were in the future, and with github and bundler there is now rarely a need to monkey patch ruby code in your applications monkey patching is the dangerousyetfrequentlyuseful technique of reopening existing classes to change or add to their behavior. The motivation behind introducing refinements is discouraging monkeypatching. Ruby has a very beautiful syntax and so it can be tempting to monkey patch a class to turn some ugly method call into something that is more readable. The reason it works in rails and it doesnt work when i am outside of the rails framework is because rails has monkeypatched a large number of the core ruby classes.
Refinements provide a way to extend a class locally. If you have a class such as telnetconnection, and you want to extend it, subclass it in a separate file and call it something like telnetconnectionextended. Indeed, when you define a new class, youre really just creating an empty class and filling it with methods. What i did notice from the ruby community was that monkey patching was both common and highlyregarded. The ability to mutate classes at runtime has been used or abused by many libraries and frameworks to decorate ruby s core classes with additional or replacement behavior. The above statement asserts that the ruby usage is incorrect but terms evolve, and thats not always a bad thing. This practice, known as monkey patching, is common in the ruby world, and since ruby 2, its been possible. Refinements ruby monkeypatching redifined red panthers.
If you really really really want to do a monkey patch in python, you can do a sortof hack with the import foo as bar technique. Feb 26, 20 similar concepts are known as selector namespaces or classboxes in other programming languages. I am aware of an alternative, but it is equally derogatory. There are many cases where its fine to monkey patch, but it should definitely not be your first weapon of choice. Before i show you how to override a class, i want to ensure that you understand that monkeypatching is not considered a good practice. It was designed and developed in the mid1990s by yukihiro matz matsumoto in japan ruby is dynamically typed and uses garbage collection. Object oriented programming is at the heart of ruby, and in this course well work on demystifying oop and how to code in an oo fashion. Monkey patching is something thats made possible thanks to the concept of open classes. The basic idea behind refinements is to make monkey patching safer in the sense that class changes of ruby core classes, for example, are only effective in specific contexts, but not on a global scale. It will often be the case that monkey patching is just the lazy developers preference over actually refactoring or implementing a known design pattern for a particular problem. Even if the runtime already contains a monkey patch with the backported functionality, we consider the method as dirty and activate the refinement for it.
I have tried monkey patching in the past to write a gem in the past that would have a string object behave like an array, but when i included it in a rails project, it all came crashing down. What i did notice from the ruby community was that monkeypatching was both common and highlyregarded. This includes the default ruby classes like string, array, or hash. Singleton classes ruby allows to modify the class of one particular object. Truthiness and equivalence variable scopes inheritance and variable scope fake operators using core libraries as a guide command vs query monkey patching. Or perhaps you need to monkey patch a class you own. Other forms of modifying classes at runtime have different names. To the point that smart, experienced hackers reach for a monkey patch as their tool of first resort, even when a simpler, more traditional solution is possible.
So there will be cases where monkey patching is still preferred. In ruby, the term monkey patch was misunderstood to mean any dynamic modification to a class and is often used as a synonym for dynamically modifying any class at runtime. Jul 11, 2008 ruby s open classes are powerful but can easily be misused. What if, for example, you decide to monkey patch ruby s string class to produce a quickfix that shortens a certain section of code in your program. Yes, i understand that you can use ruby without monkey patching but what i am wondering if the chief reason developers reach for ruby is there love for monkey patching. It also provides a compatibilitymode for older ruby versions and alternative ruby implementations that dont support refinements yet. So you search for how to moneykeypatch a class in ruby. Ruby is an interpreted, highlevel, generalpurpose programming language. This article looks at how to minimize the risk of opening classes, alternatives, and how other languages provide similar capabilities. Ruby allows you to both open previously defined classes and redefine any method.
You will learn about all of the key features of the language. One thing ive never been crazy about is monkey patching. An objectoriented program involves classes and objects. In todays tutorial well be looking at monkey patching in ruby. I would like to know the exact meaning of monkey patching in ruby. Besides personal projects and small enduser tools, a good example, i think, is activesupport. Were in the future, and with github and bundler there is now rarely a need to monkeypatch ruby code in your applications monkeypatching is the dangerousyetfrequentlyuseful technique of reopening existing classes to change or add to their behavior. So you have to have a way to quickly learn those changes when you jump into a new codebase. It supports multiple programming paradigms, including procedural, objectoriented, and functional programming.
But just like any of ruby s sharp edges, you have to take extra care when you use them. Monkey patching, for anyone who doesnt know, refers to the practice of extending or modifying existing code by changing classes at runtime. This process of changing classes runtime is known as monkey patching in the ruby community. Apr 05, 2020 ruby next only refines core classes if necessary. Compared to utility classes, its a hell of a lot more convenient, and it reads better. Refinements are designed to reduce the impact of monkey patching on other users of the monkey patched class.
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