Ruby on Rails simple examples & String Class

After the previous post, hope you successfully installed the ruby on to your machine and ready to speed up our tutorials.
Now let us see a simple math example, factorial function. How do we write a program that would calculate the factorial value of integer that we would pass.
Basically factorial is:

n! = 1                (when n==0)

   = n * (n-1)!       (otherwise)

• The simple logic that we are aware is, factorial is nothing but a recursive function call.

It means we write a function and will be calling the same function within that. So this would look something like this:

If you notice here there are lot of points to carry with us,

• You may notice the repeated occurrence of end.
• You may also notice the lack of a return statement.
  
• It is not needed because a ruby function returns the last thing that was evaluated in it. Though use of a return statement is permissible but it is not necessary here.
• ARGV is an array which contains the command line arguments, and to_i converts a character string to an integer.

Experiments:

1. What happens if I pass string as argument instead of integer?
2. At the line “12”, replace the double quote with single quote and see what happens?

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Ruby String Class:

A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String objects may be created using String::new or as literals.

Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String object.

· Methods with names ending in ``!’’ modify their receiver.

· Methods without a ``!’’ return a new String.

Ruby deals with strings as well as numerical data. A string may be double-quoted ("...") or single-quoted ('...').

· A double-quoted string allows character escapes by a leading backslash, and the evaluation of embedded expressions using #{}.

· A single-quoted string does not do this interpreting; what you see is what you get.

Examples:

If you had done the above mentioned experiments, it is easy to understand the above two points. The difference between the double and single quotes around a string. There are plenty of methods that ruby offers, they come very handy!

capitalize:

str.capitalize => new_str

This method turns the first letter of the string to upper case.

"ruby".capitalize    #=> "Ruby"

Methods with names ending in ``!’’ modify their receiver.

capitalize!:

str.capitalize! => str or nil
Modifies str by converting the first character to uppercase and the remainder to lowercase. Returns nil if no changes are made.

   a = "hello"

   a.capitalize!   #=> "Hello"

   a               #=> "Hello"

   a.capitalize!   #=> nil

Find more examples and other methods ruby supports.
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