One thing ive never been crazy about is monkey patching. Monkey patching is useful when you find yourself wishing an existing class had some useful piece of functionality that wasnt originally built into it. Ideally, we would never monkey patch like this, as it comes with some pretty serious side effects. Other forms of modifying classes at runtime have different names, based on their different intents. Monkey patching is the first step towards metaprogramming writing code which writes code. This is referred to as monkeypatching by pythonistas and some others. The ability to change the way classes behave at runtimeaka monkey patching has been used by many libraries and frameworks to decorate ruby s core classes with additions andor replacements. In fact, in a 2008 blog post by avdi grimm titled, monkeypatching is destroying ruby, he called out some of the issues with. Monkey patching is the new black in the ruby community.
A string is a sequence of one or more characters that may consist of letters, numbers, or symbols strings in ruby are objects, and unlike other languages, strings are mutable, which means they can be changed in place instead of creating new strings youll use strings in almost every program you write. Another case would be where ruby s literal syntax means that although you could subclass or wrap an object, it would be uglier. Why rubys monkey patching is better than land mines. Refinements are designed to reduce the impact of monkey patching on other users of. 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. But just like any of ruby s sharp edges, you have to take extra care when you use them. Add a variable to a class instance at runtime rosetta code. As such, this page will be updated on a regular basis to include additional information and cover emerging ruby techniques. Monkey patching in python dynamic behavior in python, the term monkey patch refers to dynamic or runtime modifications of a class or module.
When in vanilla ruby, a gem, for instance, you define a module in some file. One of the most useful among these specialities is that, in ruby, all classes are mutable. The above statement asserts that the ruby usage is incorrect but terms evolve, and thats not always a bad thing. Monkey patching is the technique of swapping functions or methods with others in order to change a module, library or class behavior there are some people with strong opinions about it. I havent, but it comes really useful when testing, to simulate sideeffecting functions or. If you are interested here is the back and forth of this problem being solved on the surrealist project.
Monkey patching is fun, but use it with care, otherwise youll end up with a twisted mess on the floor. However, its not all sunshine and rose petals in monkey patch land. And that could lead to side effect if we are not careful. If you keep your patches together, group them into modules, and handle the unexpected, your monkey patches will be as safe as they can be. 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. Rom ruby object mapper rom is an experimental ruby library with the goal to provide powerful object mapping capabilities without limiting the full power of your datastore. Example of money patching or open classes lets say we want to create a tweet object from a string object. Reopening code in this way is often known as monkey patching. Wirz on wed aug 03 2016 monkey patching is a technique to add, modify, or suppress the default behavior of a piece of code at runtime without changing its original source code. This post is about limiting the scope of monkey patches with ruby s refinements. The monkey patch ruby library one of the best, and worst, features of ruby is monkey patching, extending the languages builtin classes and modules to suit your desires.
Hal fulton gives an example of creating an oo csv parser at an exercise in metaprogramming with ruby. All source code included in the card how to organize monkey patches in ruby on rails projects is licensed under the license stated below. Some im not so crazy about and its usually areas where they tried to copy perl. When we see an opportunity to move a util method to one of the existing ruby s standard classes, thats when we open the existing ruby class and add that method there. 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. In ruby, its possible to add methods to absolutely any class including string, integer and other core classes. Monkey patching in python dynamic behavior geeksforgeeks. To illustrate monkey patching well make some changes to the good old string core class. Strings let you display and communicate with your users using text. Chance of alias overwriting existing method or new method overwriting your alias. 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. Sometimes you may need to override a method or add a new one to an existing class from a library or gem using a monkey patch.
One of the joys of ruby and html5 is that one can easily extract data from a web page with an xpath expression. The first thing you need to understand is that the purpose of refinements in ruby 2. This resource contains a collection of ruby best practices and ruby tips provided by our toptal network members. The monkeypatch fixture helps you to safely setdelete an attribute, dictionary item or environment variable, or to modify sys. Monkey patching is a powerful tool in the ruby ecosystem but wield it sparingly especially if you are going to jumble into code that does not belong to you. To illustrate monkey patching well make some changes to the good old string. Safer monkey patching in ruby thomas countz medium.
For example, the following extracts that uri of the rsd document from a weblog that supports rsd. 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. The ability to change the way classes behave at runtimeaka monkey patching has been used by many libraries and frameworks to decorate ruby s. You can read the definition in the wikipedia link i provided, but in short, it is a way to modify the behavior of a class or instance of a class at runtime without changing the source of that class or instance. For that reason, it can help revist the topic in order to get reacquainted with. One useful function that rubys string class doesnt provide by default is titleize, which takes a string and capitalizes the first letter of each word. In the above sample i tried to monkey patch the split method of string class. When you do it well, it makes your code feel more like ruby. If we were to monkey patch hash by reopening the hash class, this would be the most appropriate form of it. Building on josh and damons idea of hacking a subselect in activerecord, i wondered if you could bake this kind of functionality into activerecord. Ruby is like a sharp knife, it can be extremely effective, but its usually your own fault if you cut yourself. This includes the standard ruby classes like string, array or hash. Ruby s open classes are powerful but can easily be misused. Monkeypatchingmocking modules and environments pytest.
All users of the monkey patched class see the same changes. Where to put code when monkey patching stack overflow. What becomes more of an issue is that any plugin or any code in your ruby space can monkey patch a toplevel entity e. Why ruby s monkey patching is better than land mines. Whats the deal with monkeypatching and why is everyone. Were in the future, and with github and bundler there is now rarely a need to monkey patch ruby code in your applications. How to monkeypatch a core class in ruby on rails standard co. This is called monkey patching or open classes in ruby. How to organize monkey patches in ruby on rails projects.283 1470 1151 161 183 1106 493 154 630 1402 995 9 1218 6 1365 880 775 647 793 1359 1100 588 1314 1548 1296 1110 998 659 178 1412 1459 711 1441 421 834