Expanding and collapsing the hierarchy you can expand or collapse the hierarchy by using the expand and collapse toolbar buttons. You dont need to comb through the entire hierarchy to find a particular method. In this book, martin fowler shows you where opportunities for refactoring typically can be found, and how to go about reworking a bad design into a good one. It is not intended to be an standalone substitution of the book so if you really want to learn. Improving the design of existing code 99 edition 9780201485677 by martin fowler, kent beck, john brant, william opdyke and don roberts for up to 90% off at. Definition according to fowler, a refactoring consists of modifying code in order to.
In most cases, excessively long methods are the root of all evil. This refactoring merges a superclass and subclass into a single class. Code refactoring techniques in agile software development. This condition occurs when a developer preemptively designs a deep class hierarchy or after other refactorings have moved most of the functionality out of one of the classes. List of refactorings change function declaration 124 change reference to value 252 change value to reference 256 collapse hierarchy 380 combine functions selection from refactoring. This catalog of refactorings includes those refactorings described in my. This is the book that im proudest of, in that its had a high impact on the world of software development. Jan 12, 2018 although i bought refactoring book by martin fowler years ago it is still valid. Today refactoring requires considerable design knowhow, but once tools become available, all programmers should be able to improve their code using refactoring techniques. The refactoring techniques in this group streamline methods, remove code. It is not intended to be an standalone substitution of the book so if you really want to learn the concepts here presented, buy and read the book. However, i felt it would be best to focus this book on java because it is the language i know best.
Collapse hierarchy refactoring and design patterns. Refactoring the bible of refactoring is fowlers book, refactoring. Fowler 1999for more than twenty years, experienced programmers worldwide have relied on martin fowlers refactoring to improve the design of existing code and to enhance software maintainability, as well as to make existing code easier to understand. This catalog of refactorings includes those refactorings described in my original book on refactoring, together with the ruby edition. Jan 19, 2001 refactoring is about improving the design of existing code. Fully revised and updatedincludes new refactorings and code examples any fool can write code that a computer can understand.
Push down field, extract subclass, extract superclass. This lecture tries to summarize what refactoring is, when you need to do it, what patterns and tools are available. Sep 12, 2017 this is my summary of the refactoring. I call it one of the timeless books about coding and i consider it as a mandatory reading specially for novice programmers who are entering the field. You may deduplicate parallel class hierarchies in two steps.
Further, i provide some jguru examples to illustrate some of the concepts. Improving the design of existing code, renowned object technology mentor martin fowler breaks new ground, demystifying these master practices and demonstrating how software practitioners can realize the significant benefits of this new process. In case you arent aware of what refactoring is, ill give you fowlers definition. Those marked replaced have a refactoring with a different name in the new editions. You can expand or collapse the entire hierarchy, or you can expand or collapse individual parent members. Name should clearly communicate what they do and how to use them. This is the online catalog of refactorings, to support my book refactoring 2nd edition. This refactoring consists of when we want to include more behavior on a constructor then it normally has it. Inverses for refactorings refactoring inverse add parameter remove parameter change bidirectional association to unidirectional change unidirectional assocation to bidirectional change reference to value change value to reference change selection from refactoring workbook book. Does the class hierarchy that youre refactoring have more than one subclass. This refactoring book covers and organizes most of changes we are doing to source code every day and it greatly helps us to understand the nature of those changes at crafting level. If you are working on a software project and you need help with refactoring, let us know. Refactoring can, of course, be done with other languages, and i hope this book will be useful to those working with other languages. See this refactoring merges a superclass and subclass into a single class.
Until youve had to live with the same piece of code for a while, you will not experience the need for refactoring. Here are some examples of code refactoring techniques. While the book doesnt provide revolutionary solutions to perform refactoring you shouldnt perform major refactoring in one step anyway, a. There is also a section pointing out code smells that should motivate refactoring. But with new classes being added, making changes has become harder and harder. With refactoring you can even take a bad design and rework it into a good one. Improving the design of existing code shows how refactoring can make objectoriented code simpler and easier to maintain.
With proper training a skilled system designer can take a bad design and rework it into welldesigned, robust code. Improving the design of existing code shows how refactoring can make objectoriented code simpler and. The collapse hierarchy refactoring provides a series of steps to unify two such classes into one, simplifying the design. Improving the design of existing code by martin fowler. The opening example shifts its domain, as not that many people are familiar with a video store any more. If you have abstract classes that arent doing much, use collapse hierarchy.
Hes been applying objectoriented techniques to enterprise software development for over a decade. Mar 08, 2014 a screencast of one of martin fowlers refactoring patterns from the series called dealing with generalization. Several development environments now automate many of the refactorings described in the book. A screencast of one of martin fowlers refactoring patterns from the series called dealing with generalization. For example, if your program emulates city transport networks and you accidentally collapse the transport superclass into the car subclass, then the plane class may become. Parallel inheritance hierarchies refactoring and design. Improve the design of existing code software engineering class on main refactoring techniques and bad smells reported in the famous fawlers book slideshare uses cookies to improve functionality and performance, and to. Improving the design of existing code 2nd edition by martin fowler. Behavior has been removed, or moved elsewhere in the system, and they are almost the same entity. Collapse hierarchy is a variation of inline class, where the code moves to superclass or subclass. If so, after refactoring is complete, the remaining subclasses should become the inheritors of the class in which the hierarchy was collapsed. The heart of the book is a catalog of refactorings, organized in chapters on. Refactoring is not just any restructuring intended to improve the code refactoring. Good programmers write code that humans can understand.
A refactoring is a change to the structure of code. It is an easy concept to get started with and opens the door to much better practices such as unit testing, shared code ownership and more reliable, bugfree code in general. There are various reasons i dropped refactorings from the new edition, and i may extend this article to discuss some of these in the future. It only contains some basic concept as my understanding. The flow of the refactorings is pretty much the same. This is the book that introduced the concept of refactoring to the wider software engineering community. Without refactoring you accrue technical debt, forget what portions of code do and create code that is resistant to any form of testing. Refactoring is about improving the design of existing code. It is used when one of those classes provides little value. It is the process of changing a software system in such a way that it does not alter the external behavior of the code, yet improves its internal structure. Much of refactoring is devoted to correctly composing methods. Each refactoring step is simpleseemingly too simple to be worth doing. Changes for the 2nd edition of refactoring martin fowler. Improving the design of existing code ebook written by martin fowler, kent beck, john brant, william opdyke, don roberts.
It is not intended to be an standalone substitution of the book so if you really want to learn the concepts here presented, buy and read the book and use this repository as a reference and guide. A collapse hierarchy refactoring would be applied when you realize you no longer need a subclass. The bulk of this book is a catalog of refactorings, but there is more to it as i will explain below. Refactoring does not include any change to the system. All of these follow the broad forms of the original book. Martin fowler is the chief scientist of thoughtworks, an enterpriseapplication development and delivery company. A subtle form of duplication, this smell exists when numerous pieces of code do the same thing using different combinations of data or behavior. The vagaries of code inside these methods conceal the execution logic and make the method extremely hard to understand and even harder to change. Code refactoring is one of the key terms in software development and today i would like to talk about code refactoring. A longer list can be found in martin fowlers refactoring book, which we discussed above. Improving the design of existing code is one of those amazing books that every professional developer should have on their book shelf.
You can expand and collapse a hierarchy in any window or panel with objects in nested groups using one of the following methods. This refactoring not only simplifies the code on the callers side, but also simplifies changes if the method needs more data from the object passed by parameter on the future. Jan 01, 1999 the book is well written, provides samples, examples, diagrams, steps to follow, sidenotes, commentary, and basically everything you would need to fully understand a refactoring method. First, make instances of one hierarchy refer to instances of another hierarchy.
All was well as long as the hierarchy stayed small. Smells to refactorings quick reference guide smell refactoring unify interfaces with adapter k 247 rename method f 273 move method f 142 combinatorial explosion. Refactoring has become a fullfledged part of the software development lexicon sadly also leading to misuse. Fowler 1999for more than twenty years, experienced. Interestingly, this book predates kent becks tdd book by a few years, and beck contributed a lot to the book.
102 1351 621 237 1565 414 1069 574 1357 487 1622 1042 516 1168 1161 654 963 221 1225 183 298 493 1366 201 644 546 39 894 1323 1186 856 1263