Hashes: A Hash is a dictionary- like collection of unique keys and their values. Also called associative arrays, they are similar to Arrays, but where an Array uses integers as its index a Hash allows you to use any object type.

Hashes enumerate their values in the order that the corresponding keys were inserted.

my_hash={ "F150"=>"car" }

Create a hash

• new_hash =hash.new
• new_hash ={"John Smith" => 8}

Iterating over hashes

• for loop
• letters = [ 'a','b','c','d'] letters.each do | letter | backslash print letter end

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Array: Arrays are ordered, integer-indexed collections of any object.

Array indexing starts at 0. A negative index is assumed to be relative to the end of the array, an index of -1 indicates the last element of the array, -2 is the next to last element in the array, and so on.

To create a array

• ary= Array.new
• ary= [1,"two",3.0]

Add elements to an array

• .push method
a = ["a","b","c"] a.push("d","e","f")


• << method
sample.push(3,4,5) sample <<3 <<4 <<5

Remove elements from an array

• .pop method

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String: A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters.

Strings can store in Ruby using the String object. In addition to providing storage for strings, this object also contains a number of methods, which can be used to manipulate strings

Creating new string

• mystring=String.new
• mystring=String.new("This is my string. My name is Hello world")
• mystring=String("This is also my string")
• mystring="This is also a string"

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Integers: Integer is the basic for the two concrete classes that hold whole numbers, (Bignum and Fixnum).

• Bignum: Objects hold integers outside the range of Fixnum. Bignum objects are created automatically when integers calculations would otherwise overflow a Fixnum. When a calculation involving Bignum objects return a result that will fit in a Fixnum, that result is automatically covered.


• Fixnum: Holds Integer values that can be represented in a native machine word (minus 1 bit). If any operation on a Fixnum exceeds this range, the value is automatically converted to a Bignum.

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