Wiley Ruby on Rails For Dummies
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1. the programmer to refine her evolving requirements After several brief rounds of coding and testing the Web site was ready for public use The wolf enjoyed visiting the site because the site s look and feel reflected the way it had been designed The site was nimble intelligent and easy to use The site did the kinds of things the wolf wanted it to do because the programmer had gotten feedback on each prototype Everyone was happy for a while anyway To repay the Ruby on Rails programmer the wolf offered to repair her house s leaking roof Unfortunately the wolf had a nasty accident While he was working on the roof he fell into the chimney and landed directly into a pot of boiling water Goodbye wolf But the Ruby on Rails programmer was happy She had created a great Web site And with all the time she d saved using Ruby on Rails she was able to climb up to the roof and repair the leak herself The end Chapter 1 Welcome to the World of Ruby on Rails The Software Development Process The world changes quickly Ten years ago when I taught programming to computer professionals I wore a suit and a tie Last month I taught the same course wearing a polo shirt and khakis This tendency for things to change goes way back In the 1960s programmers and managers noticed that commercial software tended to be very buggy They analyzed large projects created by big businesses They saw software development efforts goi2. Chapter 1 Welcome to the World of Ruby on Rails In This Chapter Understanding the need for agile software development Discovering Ruby s role in agile development Finding out how Rails fits in 0 nce upon a time there were three little programmers The programmers wrote code for the World Wide Web code to give users access to a company s database The first programmer was in a hurry to write her code She wrote simple code as quickly as she could The second programmer wasn t quite in such a hurry She used the traditional Waterfall methodology a multistep process involving analysis design coding testing and deployment The third pro grammer was Careful and industrious She used a heavyweight persistence framework such as Enterprise JavaBeans She built her software to cover every possible contingency and to accommodate any future need As you might expect this story has a big bad wolf The wolf might have been a manager a client paying for the software s creation or a customer attempt ing to access the company s Web site The wolf went in reverse order visiting the careful and industrious programmer s Web site first Unfortunately the wolf couldn t log onto the industrious programmer s site Instead he got the message This site is under construction The careful industrious programmer had completed only half of her work The heavy weight persistence framework was difficult to learn and burdensom
3. Ruby is reflective A Ruby program can reflect upon its own code like a philosopher reflecting on his or her own life More specifically a Ruby program can turn a string of characters into executable code and can do this somersault during the run of a program Listing 1 1 contains an example Listing 1 1 Defining a Database Table print Enter some text STDOUT flush text_input gets puts print You entered print text_input puts print Maybe you entered some Ruby code n print I ll try to execute the text that you entered n print The result of executing your text is eval text_input Figures 1 1 and 1 2 show two different runs of the code in Listing 1 1 In each run the code prompts you to type some text Ruby does two things with whatever text you type Ruby echoes the text displays the text a second time on the screen Ruby interprets your text as Ruby code and executes the code if possible The second step reinterpreting text as code is difficult to do in other pro gramming languages Ruby makes it easy to reinterpret text as code and this ease makes life better for computer programmers Problems RI GJ Console 3 Tasks RegExp lt terminated gt reflect rb Ruby Application Ruby C ruby bin ruby ex Enter some text x 10 int x Chapter 1 Welcome to the World of Ruby on Rails ee Figure 1 2 Running the code with more com plicated input AE Problems RI Con
4. alls to straighten things out That s a danger of having more than one copy of a certain piece of information Aside from the risk of error the duplication of information means more work for everyone With traditional database programming you must track every decision carefully If you add a column to a database table you must update the description of the database in the code The updating can be time consuming and it discourages agility Also if each change to a database table requires you to dive into your code yov re less likely to make changes If you avoid changes you might not be responding to your customer s ever changing needs Let s Get Going You can read this chapter s lofty paragraphs until you develop a throbbing headache But the meaning behind these paragraphs might be somewhat elu sive Do you feel different when you switch from C or Java to programming in Ruby Does Rails really speed up the development cycle Can you create an application in the time it takes to find a Starbucks in Manhattan If you find these questions intriguing please read on 20 Part I Nuts and Bolts
5. dback as you write the letter You try to guess what the potential employer wants you to say but you can never be sure You use a formal writing style in case the employer is a stodgy old coot Now imagine using a formal style to speak to your friend If you have any questions about our next meeting at Kelly s Tavern please don t hesitate to call me at the phone number on this napkin I look forward to hearing from you soon Yours truly et cetera et cetera Using formal language with your friend would slow the conversation to a crawl You wouldn t pop your eyes open when you heard some juicy gossip Instead you d plan each sentence carefully You d think about subject verb agreement hoping you didn t offend your friend with an awkward phrase or with some inappropriate slang 14 Part I Nuts and Bolts Language isn t a neutral medium of expression Language influences the nature of the message A free flowing style encourages free flowing thought In the same way a flexible programming language complements an agile soft ware development process Why Ruby Ruby is a computer programming language You might be familiar with Basic Java C or some other programming language In certain ways all these languages are the same They all provide ways for you to give instructions to a computer Move this value from that memory location to that other location on your hard drive A computer language is a way of exp
6. e ever mentioned the methodology books again I would have cracked the books open out of curiosity But unfortunately excessive dust makes me sneeze Had I found anyone on the team who knew the methodology I probably 12 Part I Nuts and Bolts would have learned how ponderous the methodology can be No one wanted to wade through hundreds of pages of principles rules and flow diagrams And if anyone did they d read about rigid systems systems that encourage programmers to follow fixed procedures systems that don t encourage programmers to listen to adjust or to change Agility In 2001 a group of practitioners created the Manifesto for Agile Software Development www agilemanifesto org The Manifesto s signatories turned their backs on the methodologies of the past Instead they favored a nimble approach Their principles put individuals and interactions over processes and tools and put responding to change over following a plan Best of all they declared that Simplicity the art of maximizing the amount of work not done is essential According to these practitioners the proof of the pudding is in the result A process that doesn t end ina worthwhile result is a bad process even if it s an orderly well established process The Agile Manifesto s signatories aren t opposed to the discipline of software engineering On the contrary they believe firmly in the science of software dev
7. e to use Needless to say the wolf huffed and he puffed and he blew the Web site down 10 Part I Nuts and Bolts So the wolf visited the second programmer s Web site The site was up and running but certain aspects of the site didn t meet the wolf s needs In fol lowing the Waterfall methodology the second programmer had carefully planned every aspect of the project before beginning to write the code But by the time the code was ready for testing the project s requirements had shifted The second programmer was aware of her Web site s deficiencies Through extended testing and use she had learned that the original requirements were obsolete But with all the code in place the second programmer couldn t easily make major changes All she could do was fix bugs and make the code run a bit faster She promised that she d update the requirements for version 2 0 of the system But the wolf was impatient He huffed and he puffed and he blew the Web site down In desperation the wolf visited the first programmer s Web site She had built the site quickly and easily using Ruby on Rails In fact her first prototype had been up and running in two days Her co workers had tested the prototype critiqued the prototype s features and told her what they expected in the next prototype The next prototype was ready sooner than anyone expected Once again co workers tested the prototype suggested improvements and helped
8. e year 2000 teams of Java programmers have been using a framework named Struts The Struts framework addresses many of the problems described in this chapter Web development databases and other such things But the word strut means something in the construction industry A strut is a horizontal brace and a sturdy one at that Well a rail is also a kind of horizontal brace And like Ruby the word Rail begins with the letter R Thus the name Ruby on Rails In spite of the name Ruby on Rails you don t add Ruby on top of Rails Rather the Rails framework is an add on to the Ruby programming language 17 18 Part I Nuts and Bolts The following fact might not surprise you at all What separates Rails from Struts and other frameworks is agility Other frameworks used to solve the Web database problem are heavy and rigid Development in these other frameworks is slow and formal In comparison Rails is lightweight and nimble Author and practitioner Curt Hibbs claims that you can write a Rails applica tion in one tenth the time it takes to write the same application using a heavyweight framework Many people challenge this claim but the fact that Hibbs is willing to make the claim says something important about Rails Rails is built on two solid principles convention over configuration and Don t Repeat Yourself DRY Convention over configuration A Web application consists of many parts and you can go crazy conn
9. ecting all the parts Take one small example You have a variable named picture in a computer program and you have a column named image in a database table The computer program fetches data from the image table column and stores this data in the picture variable Then the program performs some acrobatics with the picture variable s data For example the program dis plays the picture s bits on a Web page One way to deal with an application s parts is to pretend that names like picture and image bear little relation to one another A programmer stitches together the application s parts using a configuration file The configuration file encodes facts such as variable picture reads data from column image variable quotation reads data from column stock_value and variable comment_by_expert reads data from column quotation How confusing With dozens of names to encode at many levels of an application program mers spend hours writing configuration files and specifying complex chains of names In the end errors creep into the system and programmers spend more hours chasing bugs Rails shuns configuration in favor of naming conventions In Rails a variable named image matches automatically with a column of the same name in the database table A variable named Photo matches automatically with a table named photos And a variable named Person matches automatically with a table named people Yes Rails understands plural
10. elopment But they don t believe in unnecessary paperwork required checklists and mandatory diagrams In other words they don t like horse puckey Databases and the World Wide Web By 2001 many businesses faced an enormous problem Computers were no longer islands unto themselves Customers visited Web sites ordered goods read headlines updated records posted comments and downloaded songs At one end was a Web browser at the other end was a database In between was lots of network plumbing The problem was to move data from the browser to the database and from the database to the browser The movement must be efficient reliable and secure Imagine millions of people working on the same problem moving data between a Web browser and a database If everyone works independently then millions of people duplicate each others efforts Instead of working independently why not have people build on other people s work Create a software framework for connecting Web browsers to databases Provide hooks into the software so that people can customize the framework s behavior An online order system uses the framework one way and a social networking site uses the framework in its own completely different way Chapter 1 Welcome to the World of Ruby on Rails 13 Throwing frameworks at the problem By 2004 there wasn t just one framework for solving the Web database prob lem There were dozens of frameworks New framework
11. mal values and then to being strings or arrays They change easily without any complicated programming techniques This flexibility makes Ruby a good language for agile software development Ruby is interpreted Many commonly used programming languages are compiled When the com puter compiles a program the computer translates the program into a very detailed set of instructions a set more detailed than the set that the pro grammer originally writes So picture yourself developing code in a compiled language First you write the code Then you compile the code Then you run the code The code doesn t run exactly the way you want it to run so you modify the code Then you compile again And then you run the code again This cycle takes place hun dreds of times a day Modify compile run You get tired of saying it inside your head In contrast to the compiled languages Ruby is interpreted An interpreted lan guage bypasses the compilation step You write the code and then you run the code Of course you don t like the results That s a given So you modify and rerun the code The whole cycle is much shorter A piece of software the Ruby interpreter examines your code and executes that code without delay Which is better compiled code or interpreted code Believe it or not the answer depends on your point of view A computer executes compiled code faster than interpreted code But as computer processing power beco
12. mes cheaper the speed of execution is no longer such an important issue So step back from the processing speed issue and think about the speed of software development With a compiled language each modify compile run cycle is three steps long compared with the two step modify run cycle in an interpreted language such as Ruby But what s the big deal How long can an extra compilation step possibly take The answer is that compilation can slow you down Compilation can be time consuming especially on a very large complex project Even a two second com pilation can be annoying if you perform the cycle several hundred times a day But aside from the time factor the compilation step distances the programmer from the run of a program Imagine writing a program in a compiled language say in C The computer compiles your program to get a more detailed set of instructions This detailed set of instructions isn t the same as your origi nal program It s a translation of your instructions Instead of executing your program the computer executes a translation 16 Part I Nuts and Bolts Ce Figure 1 1 Arun of the code in Listing 1 1 a Little to nothing gets lost in translation But the fact that the computer doesn t run your original code makes a difference in the way you think about the development cycle The immediate hands on feeling of an interpreted lan guage gives an extra lift to the agile development mindset
13. ng past deadline and over budget They saw finished products that were terribly unreliable Most computer code was difficult to test and impossible to maintain So they panicked They wrote books magazine articles and scholarly papers They theorized They devised principles and they arrived at various conclusions After years of theorizing they founded the discipline known as software engineering The goal of software engineering is to discover practices that help people write good code As disciplines go software engineering is pretty good stuff Software engineering encourages people to think about the way they create software And when people think about the way they work they tend to work better But in the 1970s software engineering focused on methodologies A methodol ogy is a prescribed set of practices Do this then do that and finally do the other thing When you re finished you have a big software system But do you have a useful software system In 1979 I worked briefly for a company in Milwaukee On the day I arrived the team manager pointed to the team s methodology books The books con sisted of two monstrous volumes Together the volumes consumed about six inches of bookshelf I remember the team manager s words as he pointed a second time to the books That s what we use around here Those are the practices that we follow I spent several months working for that company In all those months no on
14. ressing instructions in a precise unambiguous manner What makes Ruby different from so many other computer programming lan guages In what way does Ruby support agile development Here s the answer Ruby is a dynamically typed interpreted reflective object oriented language That s a great answer but what does it mean Ruby is dynamically typed In many languages you have to declare each variable s type You write int date date 25092006 The first line tells the computer that the date must store an integer a whole number a number without a decimal point a number like 25092006 Later in the same program you might write date September 25 2006 But the computer refuses to accept this new line of code The computer flags this line with an error message The value September 25 2006 isn t an integer In fact September 25 2006 isn t a number And because of the int date line the non Ruby program expects date to store an integer The word int stands for a type of value In a statically typed language a vari able s type doesn t change In contrast Ruby is dynamically typed The following lines form a complete valid Ruby program 25092006 September 25 2006 date date Chapter 1 Welcome to the World of Ruby on Rails 15 Yes this program doesn t do anything useful but it s a program nevertheless Ruby s variables can change from being integers to being deci
15. s In Rails most configuration files are completely unnecessary You can create configuration information if you want to break Ruby s naming conventions But if you re lucky you seldom find it necessary to break Ruby s naming conventions Chapter 1 Welcome to the World of Ruby on Rails 9 Don t Repeat Vourself DRY Another important Rails principle is to avoid duplicating information A tradi tional program contains code describing database tables The code tells the rest of the program about the structure of the tables Only after this descrip tive code is in place can the rest of the program read data from the database But in some sense the description of a database is redundant A program can examine a database and automatically deduce the structure of the database s tables Any descriptive code simply repeats the obvious Hey everyone There s a gorilla in the room And there s an image column in the photos database table So what else is new In computer programming repetition is bad For one thing repetition of infor mation can lead to errors If the description of a database is inaccurate the program containing the description doesn t work My HMO asks for my address on every claim form But my address hasn t changed in the past ten years Occasionally the folks who process the claim forms copy my address incorrectly They mail a reimbursement check to the wrong house Then I make ten phone c
16. s with names such as Enterprise JavaBeans Spring Hibernate and NET tackled pieces of the problem But most of the aforementioned frameworks had a serious deficiency They didn t lend themselves to agile software development Software created with one of these frameworks was fairly rigid Planning was essential Changes were costly What the world needed was a different framework a framework for agile developers The world needed a language that didn t put programmers in a box The world needed software that could shift with a user s shifting needs Let the major corporations use the older heavyweight frameworks An entrepreneurial company thrives with a more versatile framework A small to medium size company needs Ruby on Rails Along Comes Ruby on Rails Think about your native language the language you speak at home Divide the language into two styles You use one style when you speak to a close friend Hi buddy You use another more formal style when you write to a potential employer Dear Sir or Madam Talking to a close friend is an agile activity You listen intently but occasion ally you interrupt If your friend says something intriguing you take time out to ask for more details You don t try to impress your friend You tune care fully to your friend s mood and the friend tunes to your mood In contrast writing a business cover letter is not an agile activity You don t get fee
17. sole 3 Tasks RegExp 1 lt terminated gt reflect rb Ruby Application Ruby C ruby bin ruby exe reflectrb Enter some text prod 1 S times x print prod x 1 You entered prod 1 S times x print prod x 1 Maybe you entered some Ruby code I ll try to execute the text that you entered The result of executing your text is 1 2 6 24 120 Ruby is object oriented I describe object oriented programming OOP in Chapter 6 So I don t want to spoil the fun in this chapter But to give you a preview object oriented pro gramming centers around nouns not verbs With object oriented program ming you begin by defining nouns Each account has a name and a balance Each customer has a name an address and one or more accounts After describing the nouns you start applying verbs Create a new account for a particular customer Display the account s balance And so on Since the late 1980s most commonly used programming languages have been object oriented So I can t claim that Ruby is special this way But Ruby s object oriented style is more free form than its equivalent in other languages Again for more details on object oriented programming in Ruby see Chapter 6 Why Rails Rails is an add on to the Ruby programming language This add on contains a library full of Ruby code scripts for generating parts of applications and a lot more The name Ruby on Rails is an inside joke Since th
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