An agile primer addisonwesley professional ruby series kindle edition by metz, sandi. A monkey patch is a way for a program to extend or modify supporting system software locally. Ruby facets the premiere collection of general purpose method extensions and standard additions for ruby. Ruby is, for better or worse, an extremely flexible language. The monkey patch is a way for a program to extend or modify system classes locally in an objectoriented language. Interfaces are statically checked python duck typing. Check out the toptal resource pages for additional information on ruby. An agile primer addisonwesley professional ruby series. You can monkeypatch any code, it doesnt matter whether its your own code or not. To be fair monkey patching in ruby and js land is also unsafe and can be nutty but they dont have compilers. It is a treelike hierarchy, where we have parent objects and child objects.
Monkey patching is the dangerousyetfrequentlyuseful technique of reopening existing classes to change or add to their behavior. Granted its not just bc ruby permits monkey patching and other quirky programming techniques. This chapter will take you through all the major functionalities related to. A common assumption in objectoriented programming is that native. Programming classes and objects in ruby launch school. Monkey patching a monkey patch is a way for a program to extend or modify supporting system software locally affecting only the running instance of the program. Written by sandi metz, it explains objectoriented design ood using realistic, understandable examples. I think its great for creating dsls domain specific languages, because you can write code that is very terse, but does a lot. A creative developer can do all sorts of interesting things. In oop, the programmer focuses on the content of that object and how that object behaves.
This is here just to demonstrate the power that ruby gives you along with. Our best tips and practices are trying to fill the gap. The result is a gap between module systems for objectoriented languages on one hand, and the. So, rather than make one more academic blog post about the four principles of oop i will take you through a hands on example written in ruby.
Ruby claims to be an object oriented scripting language. A monkey patch is a way for a program to extend or modify supporting system software locally affecting only the running instance of the program. Monkey patching is the new black in the ruby community. All things being equal, i prefer using traditional oo techniques with a sprinkle of functional programming goodness. Lets get started most academics approach object oriented discussions with tonka toys and furry kittens. Use features like bookmarks, note taking and highlighting while reading practical objectoriented design in ruby. Im actually really surprised go doesnt just let you add methods to arbitrary types that you dont own. One of the great things about learning a new language is learning. Programming languages have procedural programming, functional programming and objectoriented programming paradigms. It is often used when monkey patching an existing method to tailor its functionality to the.
Ruby is not more oop because it can monkey patch classes i agree its more about dynamism, but because it was designed from the ground up to be a pure oop language. To know which object you are at the moment, one may use the keyword self. Each ruby class may have only one method of a given name. This is distinctly different than traditional subclassing because you are not creating a new class, instead, you are reopening an existing class and changing its behavior. On ruby as an object oriented programming language has these concepts. One answer is to monkey patch, but by now i think we all know that that.
The language is dynamic, reflective, and object oriented, but still requires experience for a developer to be able to harness their true power. Every value in ruby is an object, even the most primitive things. Before insulting a language because its not possible to monkey patch in it, think about. This article looks at how to minimize the risk of opening classes, alternatives, and how other languages provide similar capabilities. Ruby is, like many other popular languages, an objectoriented programming language. A good ruby developer should not only be able to solve problems using ruby as the programming language but also be familiar with the concepts behind ruby and have. Until you hit weird bugs because a patch changed hash. The design paradigm known as objectoriented programming oop is so at the core of ruby and modern programming that its kind of glaring that ive gotten this far in the book without really explaining to it. However, in ruby an object usually refers to a particular instance of a class. Add a variable to a class instance at runtime rosetta code. Ruby recognizes that this is a setter method and allows us to use the more natural assignment syntax.
This is pretty much the worst way to do it, but id learned so many programming languages by then that it didnt hinder me too much. 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. Objects, ruby classes and mixins are the topics today. Practical objectoriented design, an agile primer using ruby poodr is a programmers tale about how to write objectoriented code. Microsoft powerpoint lecture0408ruby compatibility mode author. Rubys ability for metaprogramming allows a programmer to modify methods in the languages standard library during runtime, a practice known as monkey patch ing. Even a class itself is an object that is an instance of the class class. Object oriented programming, often referred to as oop, is a programming paradigm that was created to deal with the growing complexity of large software systems. Rubys pure objectoriented approach is most commonly demonstrated by a bit of code which applies an action to a number. Object oriented programming in ruby is at once elegant and simple. Basically, in ruby and in pretty much all singledispatch based oo languages, a method is bound to a specific receiver object, called self in ruby.
There have been a variety of answers to that question, all. When monkey patching an instance method, can you call the. Monkeypatching is possible in objectivec by using categories. As a language maniac and oo fan for 15 years, i really wanted a genuine objectoriented, easytouse scripting language. I dont actually think that monkey patching is destroying ruby, but i do. There are many cases where its fine to monkey patch, but it should definitely not be your first weapon of choice. But i didnt like it, because i didnt think it was a true objectoriented language oo features appeared to be addon to the language. Programmers found out very early on that as applications grew in complexity and size, they became very difficult to maintain. Monkey patching is dangerous, when used without responsibility. This can lead to possible collisions of behavior and subsequent unexpected results, and is a concern if done recklessly for code scalability. Rubys almost pure objectorientedness, concise syntax and praising of.
Ruby is a pure objectoriented language and everything appears to ruby as an object. Flexible ruby value object initialisation dev community. Why rubys monkey patching is better than land mines. And a great deal of the rails framework itself is based on this ability. To call anything object oriented can make you sound pretty smart. Poodr is a practical, readable introduction to how ood can lower your costs and improve your applications. You may find enlightening this discussion about rubys open classes and the openclosed principle. One of the principles of objectoriented design that you might pick up.
Roleplaying as an object in your program is an integral part of objectoriented programming. In many objectoriented languages objects form a hierarchy. The definition of the term varies depending upon the community using it. If the developer wishes to accept different sets of parameters they must splat the arguments and branch within the method. In this part of the ruby tutorial, we will talk about objectoriented programming in ruby. I have chosen to implement my bot in clojure as a good excuse to learn the language with a problem that has some meat to it. Hal fulton gives an example of creating an oo csv parser at an exercise in metaprogramming with ruby. This is referred to as monkeypatching by pythonistas and some others. Objectoriented programming calls properties by the name instance variables and actions are known as methods. The secret to rails oo design literate programming. A developer notebook on applying classic objectoriented principles to ruby on rails projects.
The one thing that it did do, however, was give me a slightly twisted sense of how to. 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. Rubygems module count soon to surpass cpans slashdot. In below text, well use term monkey patch for changing behavior of some. To make things happen using ruby, one always puts oneself in the place of an object and then has conversations with other objects, telling them to do stuff. There is a ruby hiring guide, ruby job description, and ruby interview.
Even though i like ruby, i feel monkeypatching is a tool of last resort to get things done. Or perhaps you need to monkey patch a class you own. Hanamiutils lightweight, nonmonkeypatch class utilities for hanami and ruby app. Hanamiutils lightweight, non monkey patch class utilities for hanami and ruby app. Interactive ruby our roadmap objectoriented programming variables reusing variable names things on the right go first builtin data types numbers strings true, false, and nil symbols arrays hashes objects, classes, methods objects have classes. The ruby and ruby on rails online test assesses candidates knowledge of programming in the ruby language as well as their knowledge of the ruby on rails web application framework. This is useful when the methodsvariables of an instance are based on a data file that isnt available until runtime.
Were in the future, and with github and bundler there is now rarely a need to monkey patch ruby code in your applications. Ruby s open classes are powerful but can easily be misused. At some point in the 1990s this paradigm started to become more and. Every bit of information and code can be given their own properties and actions. The nature of ruby, how you can modify any object in memory, or monkey patch a class, can lead to some very elegant solutions. There is lots of information out there about object oriented programming oop, but if your like me i find most of this information to be much too abstract. Why ruby s monkey patching is better than land mines. What if, for example, you decide to monkey patch rubys string class to produce a quickfix that shortens a certain section of code in your program. Yet it is an expression of the freedom that ruby gives us. Download it once and read it on your kindle device, pc, phones or tablets.
Other forms of modifying classes at runtime have different names, based on their different intents. Ruby is a dynamic language with a focus on simplicity and productivity. In computer science, an object is a location in memory having a value, and and can therefore be anything from methods to classes to functions. The prescriptions are appropriate both as rules for novices and as guidelines for experienced professionals. Monkey patching is the practice of adding methods to or altering rubys core classes.
Prepend and super for elegant monkey patching sebastian royer. This video is about poodr chapter 1 where we talk about what objectoriented programming is, why its important, and the design process. Hamster efficient, immutable, and threadsafe collection classes for ruby. On the other hand, the main advantage of ruby on rails is that it is an interpreted language. In a nutshell, objectoriented programming sees the world as data, modeled in code by objects. Extending classes is a key part of object oriented programming. Praise for the first edition of practical objectoriented design in ruby meticulously pragmatic and exquisitely articulate, practical object oriented design in ruby makes otherwise elusive knowledge available to an audience which desperately needs it. Practical objectoriented design in ruby chapter 1 youtube.
463 1249 27 1447 767 1119 334 1418 1206 939 1001 567 39 990 530 391 1189 704 554 907 149 959 1416 384 919 1494 794 1421 1139 686 349 857 1130 1046 494 113 1272 1134