Ruby Commands

Ruby Commands

String	Text, Alphabets should be entered in inverted commas
Array	List of numbered items in a square bracket, separated by comma. [0,1,2]. Remember position in array starts from 0 and not 1.
Puts	Output, execute
Print	Prints on screen
Conditions	False, Nil    True,0
**	Raise to power
%	Gives us the remainder of the division
==	Test whether the condition holds true of false
.eql?	Checks equal in absolute term 3.eql?3.0 (False)
!=	Not Equal to
If	Checks the argument. Each if to have corresponding end
Else	Used for false return in If formula.
Elsif	Checks multiple if conditions
Unless	Executes the command if condition is false
&&	And, checks both conditions in If argument
||	Or, evaluates either of the conditions as true
!	Not, reverses the output i.e true conditions is responded as false
Case, when	Checks the value of case and gives result based on when conditions. Each case to have corresponding end.
While	Keeps on executing the code till statement holds true.
Untill	Keeps on executing the code untill statement holds false
(..) Two dots	Inclusive range. When used with square brackets it presumes the given numbers as positions and not numbers of the range.
(…) Three dots	Exclusive range
to_a	Convert range into array
For x in (..)	Returns values of that range in a loop
Loop do	Create a loop
Break	To stop a loop
Next	Skip iteration in the loop
<<, .push	To put a value in the end of the array
Pop	Removes the last value in the array
.insert (position number, value)	Inserts the value at the desired positon in the array list
Delete_at (Position number)

Array Manipulations           

&	Find common elements in brackets
| and .uniq!	Removes duplicates in a array
.reverse
.reverse!
.length and .size	Number of elements in array
.sort	Sorts the elements in array
.freeze	Freezes array from being modified
.include?(obj)	Searches for Obj in array and returns true if present.
.min	Returns the minimum value in the array
.max	Returns the element with maximum value
-1	Returns the last element of the array

Hash Manipulations

Month = {“Jan”=>“January”}	Hash = {Key=>Value}
A=:10,A:10	Key=:Symbol/Value. These cannot be changed.
hash.DELETE(:key)	Deleted particular key in the hash
hash.INDEX(:value)	Reverse searches and gives key for the value specified. Returns nil if not found.
Hash.INVERT	Keys become value and values becomes keys
Hash.KEYS	Returns the keys in the hash
Hash.values	Returns the values in the hash
Hash.length	Returns the length of keys in the hash as Integer

.each  | |	Converts each array item into a variable.
Times	Creates loop for prescribed number of times
.downcase!	Convert all letters into lowercase

Methods

Def X  puts Y   end	Define a method. Renames/Processes a thing. Here X is called parameter.
Gets.chomp	Used to take user input
Return	Prints the called value. Anything mentioned after return and before end is not counted.
Private	Method defined after it won’t be available outside that class.
Rand()	Pick random number.

Types of variables

Local	Available only inside the loop
Global	Prefixed with $ sign. Can be changed from anywhere in the code.
Instance object.methodname (getter method)	Executes that method defined in the class. Fetches the variable
To_s	Is activated by default when calling for the object for the class. Prints object class.random encoding of the object id. If the same is defined as a method, it can give information in a format.
Set_name=(name)	Object.set_name will change the already attached variable to the object.
@	To create Instance variable. Tagging object/identity to variable. These are accessible from anywhere in the project.
Class	Outlines what an object would be
Classname.NEW	To add new objects to the class
@@	Class variable. These are used to get information about class and not individual objects.
CAP,PI	Constant that do no change value
Class::CONSTANT	To call for the constant
Initialize	Method defined inside a class. It is called for every object created.
attr_accessor:Object name, objectname, objectname
Self.object	Class method.For calling the method within class. For defining the method which can be called along with class.
Show_info

Class

<	Subclass (derived class) < Superclass (Base class) Subclass inherits/uses/gets the methods and attributes. Base class may have multiple sub class. But Sub class cannot have multiple superclasses. However any method of the same name defined in subclass will overrule the method definition of main class.
Super	Calls for corresponding method of main class. Allows subclass method to give output after main class method output.
Module	Collection of method that can be used in other classes. An object cannot be created from module.
Module::Class.new
Module.classmethod	Self.method
Include	To include module into class.

Class can inherit from only one class but can include any number of modules.

Struct	Structure
Require ostruct	Open structure
Maths	Some predefined Maths command
Time	Some predefined Time command.
Proc
Lambda
Do	Define a method
_proc.call	To call a method created using Proc
call

File.new(“Filename”, “Accesspermisions”)
R	Read only
R+	Read + Write
W	Write only
File.file?(“Filename”)	To return true if the file exists and false if it does not exist.
File.open(“Filename”, “Accesspermisions”)
File.read(“filename”) File.readable?
File.readlines (“filename”)
File.close	Remember to close the file after performing operations.
File.delete(“filename”)
F.size	Sixe of file
File.writable?
File.executable?