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Amin Bandeali


If we doubted our Fears instead of doubting our dreams, Imagine how much in life we’d accomplish. - Joel Brown

Filed under: development

What is Ruby and Ruby on Rails (RoR)?

What is Ruby?

Ruby is a pure object-oriented programming language with a super clean syntax that makes programming elegant and fun. Ruby successfully combines Smalltalk's conceptual elegance, Python's ease of use and learning, and Perl's pragmatism. Ruby originated in Japan in the early 1990s, and has started to become popular worldwide in the past few years as more English language books and documentation have become available.

What is Rails?

Rails is an open source Ruby framework for developing database-backed web applications. What's special about that? There are dozens of frameworks out there and most of them have been around much longer than Rails. Why should you care about yet another framework? What would you think if I told you that you could develop a web application at least ten times faster with Rails than you could with a typical Java framework? You can--without making any sacrifices in the quality of your application! How is this possible? Part of the answer is in the Ruby programming language. Many things that are very simple to do in Ruby are not even possible in most other languages. Rails takes full advantage of this. The rest of the answer is in two of Rail's guiding principles: less software and convention over configuration. Less software means you write fewer lines of code to implement your application. Keeping your code small means faster development and fewer bugs, which makes your code easier to understand, maintain, and enhance. Very shortly, you will see how Rails cuts your code burden. Convention over configuration means an end to verbose XML configuration files--there aren't any in Rails! Instead of configuration files, a Rails application uses a few simple programming conventions that allow it to figure out everything through reflection and discovery. Your application code and your running database already contain everything that Rails needs to know!

via Posterous Post v0.13 source: http://oreilly.com/ruby/archive/rails.html

What are Lambda Expressions?

Lambda Expressions provide a more concise, functional syntax for writing anonymous methods. They end up being super useful when writing LINQ query expressions - since they provide a very compact and type-safe way to write functions that can be passed as arguments for subsequent evaluation.

The easiest way to conceptualize Lambda expressions is to think of them as ways to write concise inline methods.  For example, the sample I wrote above could have been written instead using C# 2.0 anonymous methods like so:

Both anonymous methods above take a Person type as a parameter.  The first anonymous method returns a boolean (indicating whether the Person's lastname is Guthrie).  The second anonymous method returns an integer (returning the person's age).  The lambda expressions we used earlier work the same - both expressions take a Person type as a parameter.  The first lambda returns a boolean, the second lambda returns an integer. 

In C# a lambda expression is syntactically written as a parameter list, followed by a => token, and then followed by the expression or statement block to execute when the expression is invoked:

params => expression

So when we wrote the lambda expression:

p => p.LastName == "Guthrie" 

we were indicating that the Lambda we were defining took a parameter "p", and that the expression of code to run returns whether the p.LastName value equals "Guthrie".  The fact that we named the parameter "p" is irrelevant - I could just have easily named it "o", "x", "foo" or any other name I wanted.

Unlike anonymous methods, which require parameter type declarations to be explicitly stated, Lambda expressions permit parameter types to be omitted and instead allow them to be inferred based on the usage.  For example, when I wrote the lambda expression p=>p.LastName == "Guthrie", the compiler inferred that the p parameter was of type Person because the "Where" extension method was working on a generic List<Person> collection.

Lambda parameter types can be inferred at both compile-time and by the Visual Studio's intellisense engine (meaning you get full intellisense and compile-time checking when writing lambdas).  For example, note when I type "p." below how Visual Studio "Orcas" provides intellisense completion because it knows "p" is of type "Person":

Note: if you want to explicitly declare the type of a parameter to a Lambda expression, you can do so by declaring the parameter type before the parameter name in the Lambda params list like so:

via weblogs.asp.net

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