Ruby - Quick - Guide

Ruby - Quick - Guide

Sample Ruby react Application

yarn install
bundle install
rails s `
the root passowrd for mysql is set to password

documentation

get ruby docs using gem docs ri String#upcase ruby information on String -> upcase

Ruby Basics

Objects

everything is Object
Object have attributes -> object is an instance of Class
attributes are what make them diffrence
they have behaviour (mont add mroe if limit is full)
. method calls a behvaoiur of the object

variable

red = 1 object red with have value 1
$ global variable
@ instance variable
@@ class variable

Numerics

interger to_i
floths to_f
abs
ceil
floor
round

String

+ add strind
<< append
reverse
capitalize
upaces
downcase
length string interpolation(JS LITTERALS)
escape "
"red car"""s"??? use backslash as escape helper
ONLY WORKS WITH DOUBLE QUOTES
"let\'s"
\n new line
\t tab
"#{var}"

Arrays

defiend in [] brackets,
can mix object types
zero index
apprend end of array <<
array methods
arr.length or x.size,
x.rverse,
x.shuffle
! -> powerul version of that method
x.reverse! -> reverse and assign.
x.uniq -> uniq items in the array
x.compact -> remove any nills in array
x.flatten -> aray will flattern all array within array are set as sinfle dim
x.include?(3)-> true or false
x.delete_at(3)-> deleted at 3rd index
or by name x.delete(Qasim')
y = x.join('~') => "567353~567~56735~2~3~~5673~56~567353~~~Abu~Qasim~4"
push pop shift unshift
add + substract -

Hashes

unordetrred collection
tracked useiong object
key-value
Hash methods
looked up by label
unique hash key
{}
specify the index
comma delimated list of key value pairs
car = {'1'=>'2', 'color'=>'red', ...
car['1'] -> 2
car.keys
car.values
car.length, car.size
x.has_key?('a')
has_key?
hash short hand x={red:"2", ...
Does not work with numbs
can use integer but not using short hand notaion

Symbols

cannot be eeditedw
begins with colon
all lowercase
:car
better momoenry and cannot be edited
same item in memory
doesnt garbnage collect often
KEY IS ALWAYS SYMBOL

BOOLENA

`TRUE
X.EM

Ranges

inclusive range 1..10 1 to 10
exclusive range `1...10`` 1 to 9
.begin -> first
.end -> last
inlcude?
Trick array out of range -> x=[*i]

Constants

All UPPERCASE
MAX_SCORE = 100
FIRST letter is contant

nil

nothing
x.nill?
! in front means does it have a vlue.

Control Structure

if else if

if boolean
elsif boolean
else boolen
end

unless

same as if not -> !

unlsss boolen
end

case

case with boolean

case
when boolean
when boolean
else
end

case with compariosn

case value
when a
when b
when 1..3
else
end

sortHand

if else boolean ? resul1 : result2 true -> result1 flaee -> result2
or operator x=y||z use y or default to zero x||=y if x has value x else x = y x=y unless x

loops

control method
- break
- next
- redo

loop do
break if bool
some calc
end


while until

while bool

end
untill bool
end


loop do
    break if count < 5
    puts "Count donwn #{count}"
    count-=5
end

while count > 5
    puts "Count donwn #{count}"
    count-=5
end

x = 1..10
x= x.to_a
until x.empty?
    f=x.shift
    puts x[2]
   puts "VALUE  #{f.to_s.upcase}"
end

itirators

perform code on each item

  5.times {puts 'hello'}
  1.upto(5) {puts 'hello'}
  3.dwonto(1) {puts 'hello'}
  (1..5).each {puts 'hello'}

block var |var|
Number: times, upto, downto, steps
Range : each, steps
String : each_line, each_char, each_byte
Array : each, each_index, each_with_index
Hash: each, each_key, each_value, each_pair

Best Practices

Sheband line #!/ur/bin/env ruby <- tells what to run in

Exit a running script

Ctrl + C
exit, exit!
abort (msg)

Input and Output

output

puts has a /n extra line return
print inpout
gets input = gets
chop removes last cahr of String
chomp removess last char of a strin if its new line

Enumerable -> can be counted

array hash ranges string
count
each
do ----> end
e.times { }
Scope -> block var has score

code block 'do end'

single line block use {}

once the block finishes the block var finishes with it

find methods

k= 1...100
# find/detect
 k.find {|n| n%5==0}
 => 5
# findall / select
k.select {|n| n%5==0}
 => [5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100]

# any none all one
 k.any? {|n| n> 100}
 => false
k.none? {|n| n> 100}
 => true

 # delete_if
y=*k
y.delete_if {|n| n%4==0}
 => [1, 2, 3, 5, 6, 7, 9, 10, 11, 13, 14, 15, 17, 18, 19, 21, 22, 23, 25, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 50, 51, 53, 54, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89, 90, 91, 93, 94, 95, 97, 98, 99]

Map/collec

OldArray -> itirateds -> code blaock on them -> add result of the block to new array
num of item in = num of item out
map always returns an arry -> use each to chenge to hash
avoide using puts
using ! will change the orignal array

z = y.map {|n| n.even? }
 => [false, true, false, true, false, true, false, true, false, true] 
y
 => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

inject/reduce methods

accumulator

bloack for using accumulation
ruby : memo
itirations cahnges value of memo passed {accumulation}
result passed
starting vlaue passed in inject(10)

y.inject {|memo, n| memo+'~Qasim~'+n}
 => "a~Qasim~b~Qasim~c~Qasim~d~Qasim~e~Qasim~f~Qasim~g~Qasim~h"

Sort <=> sapceship operator

sort tells which way to move items

k = ["qasim", "red", "vanlue5", "sum", "  n"]
=> ["qasim", "red", "vanlue5", "sum", "  n"]  
k.sort!
=> ["  n", "qasim", "red", "sum", "vanlue5"] 
k.sort {|v1,v2| v2.length <=> v1.length}
=> ["vanlue5", "qasim", "  n", "red", "sum"]

sort_by -> sort absed on zize or length
reutrus an array

merge methods

used for hashes

can merge two hashes together
rules on meger can be provide

k 
 => {:a=>23, :b=>34, :c=>"qasim", "a"=>22, :y=>"qasim\"\nk\nk\n"} 
 y
 => {:a=>"23~Q~", :b=>"34~Q~", :c=>"qasim~Q~", "a"=>"22~Q~", :y=>"qasim\"\nk\nk\n~Q~", 44=>"rr"} 
y.merge(k)
 => {:a=>23, :b=>34, :c=>"qasim", "a"=>22, :y=>"qasim\"\nk\nk\n", 44=>"rr"} 
k.merge(y)
 => {:a=>"23~Q~", :b=>"34~Q~", :c=>"qasim~Q~", "a"=>"22~Q~", :y=>"qasim\"\nk\nk\n~Q~", 44=>"rr"}

Ruby custom methods

call methods DRY (don't repeat yourself)

Scope ...

cant use outsside var inside def block

a = 10

def abc
 puts a 
end

# a not defined.

pass values as args or set instance varibale
optioal args

retun value

by defult ruby retursn last vlaue of the operation
return more than one vlue
- reutnr it as an array or ahsh

pig lating

---------------------------

Ruby Classes !!!1

---------------------------

Define calsses

template of state and behaviour
attribute -> state
methods -> behaviour

Class CamleCaseName  

end

creating instance
c = CamleCaseName.new
c2 = CamleCaseName.new

attributes

values that pesit indi and instance of a class
properties of a an object 'car is greeen'
@instace var it persisits through the instace

Readed and Writer method

getter and setter methods

Ruby

# get_noice 
def noise
 @noice 
end
# set_noise
def noise = (value)
@noice = vlue 
end

Attribaute methods

atte_*methods
- instd of set get we just use Symbols
attr_reader :noice same as get_noice
to get and set we use attr_acessor
self! passed through a method

  def noise=(value) 
      @noise = value+'33'
  end #value33
  def cranky 
      @noise = 'cra ky'
  end #cra key
  def cranky1 
      self.noise = 'cra-ky'
  end #cra-ky33

method acess calls

restricet acess methods
public anyone
private can only be called from within the calls
protected can be called by instance of class and its subclasses
helpermethods

class ...
methods ..

...

private 
-- alll privaste mehods here

only allwo acess to methdos when necessory

initialize methods

default methjods whenever an instqace of class is created
methods initizlize get automatically called

Challange

Class methods

class specefic behaviours
user self for class methods
class methods Array.new
instance methods Array#size

class attributes

properties related to class genrally
shared by all instances, as its stored in the class
calss methods use > class attr uses
uses double @ @@var

class Animal

    attr_accessor :noise, :color, :legs

    # def noise
    #     @noise
    # end

    @currentAnimal = ['some animal']
    @currentTotal = 0
    @@addedAnimal = ['some anumals']
    @@addedTotal = 0

    def initialize(options={})
      @noise, @color, @legs = options[:noise] || "noise",  options[:color] || "color", options[:legs] || " legs"
      @@addedTotal +=1
      @currentTotal = 1
      @@addedAnimal << self

    end

    def self.types 
        @@addedAnimal
    end


    def self.total 
        @@addedTotal 
    end

end

puts ''
a1 = Animal.new 
a2 = Animal.new 
a3 = Animal.new 
a4 = Animal.new 

puts '----------@@addedTypes-------------'
puts Animal.total

### ----------@@addedTypes-------------
### 4

Class Reader Writer methods

same care createing reader writer for instace var
no attr_accessor for class methods

Radio challange

class Radio
    attr_accessor :volume, :frequency 
    attr_accessor :band

    @@fm_freq = 88.0..108.00
    @@defaultFmFreq = 95.5
    @@am_freq = 540.0..1600.00
    @@defaultAmFreq = 1010.0

    def self.am 
        Radio.new(band: 'AM')
    end

    def self.fm 
        Radio.new(band: 'FM')
    end

    def initialize(options={})
        @band = options[:band] || 'FM'
        @volume = options[:volume] || 5
        @frequency = default_freq
    end



    #  volume setter condtion cannot go below 1 and above 10 
    def volume=(value)
        return if value <1 || value > 10 
        @volume = value 
    end

    def crankUp
        @volume = 11
    end

    def Volstatus 
        "Volume : #{@volume}"
    end

    # Frequency FM 88 to 108 AM 540 to 1600 
    def  frequency=(value)
        return if @band == 'AM' && (value <540 || value > 1600)
        return if @band == 'FM' && (value <88 || value > 108) 
        @frequency = value 
    end


    def status 
        "Freq #{@frequency} --  Ban  #{@band} -- vol  #{@volume}"
    end


private 

    def default_freq 
       @band == 'FM' ? @@defaultFmFreq : @@defaultAmFreq
    end 


end

r1 = Radio.fm
r1.crankUp
r1.volume = 25
r1.frequency = 1000
puts r1.status 

r2 = Radio.am
r2.volume = 25
r2.frequency = 24
puts r2.status
puts r1.Volstatus
puts r2.Volstatus

# Freq 95.5 --  Ban  FM -- vol  11
# Freq 1010.0 --  Ban  AM -- vol  5
# Volume : 11
# Volume : 5

Class inheritance

attribute inheritance
Animal -> inherit behviours calss subclass < Animal

-paents must exisit before child inheritds

DRY
- can inheritt commone set of behaviour

oversire and exrtend

as kids you can override or add new moehtods

Acess super calss from child class

call parents mwthods
- setup and then call pareent s
- fall back to emthods ? super -> CALL THE PARENT
proive ars to super

DATE and TIME

time is in nofsecods since jan 1 1970
same as unix time
Time.now

Date class

just focus on Dates

Datetime class -> sub class of date time

just focus on Dates

Date time challange

Namespacing

conflicts with same Name
avoide conflicts in naming
wrap it in module call it using the module
module A -> class Date something = A::Data.new
prevent conflics with tuby or somialr class
open source code us it mostly

Mixins

only one SUPERCLASS -> only one parent
module paakage up sahred functionality
modules are then mixed into class
DRY
SHARED FUCNTIONALORTY
ADDRESS-> USED BYY person, driver, cusotmer
module -> include moduleName

when to use what ? 4

Load Require and Include

Load: loads a source finishes
Require : smae as load - only one time
require - full path
- require_relative : laods realitve tot he file
include 'includes module in classes' others usee this dierrently

challange

Class ToDoList includeing enumarable module
to use enumrables as mixins we must define each metdod

ECEPTIONS Begin Rescue End

we raise and Exceptions
exception bubble up till orignal call
Handle specific exception using class name
rescue ZeroDivisionErro put commma to add oanther exception
Exception methods use hashRocket
e.backtrace -> file, line and where the exception was raised
Raise Exception! default Runtime.
Raise with errorName raise ArgumentError
Build custom exception class
- inherit exception
  - class new NewErroe < StandardError

begin 
resue => e 
puts "#{e.class}, #{e.message}...#{e.backtrace}"
end

Rails

first looks up public

creating controller and views

rails g <controllrtname> <viewname1> <viewname2>..... this will create controlelr for all the views specidied
controller has action within it for every view
within action you could use
redirect_to(:controller
Link to other pages link_to (text, target) use @ to declare instace var that are accssibel by all of template
contorller acessing prams
@id=params[:id]
all params are string
CRud actions
Rest HTTP
to hacve these routes added we use shorty notition
delete is not added by default
so we use
sending email - use mail to mail_to('[email protected]' under erb tag
RESOUES FULL ROUTES HELPER

FORMS - FORM_FOR HELPER

Routes

Simple match route : can use get qasim/index or simply match 'qasim/index', :to => 'qasim#index', :via => :get' controller#action
Default route : :controller :action :id get ':controller(/:action(/:id))' or match ':controller(/:action(/:id))', :via=>:get parenthesis are optional
root route : route to root of app root 'demo#index'
resourceful route :

varibale vs instance variable (@)

are scoped to that .rb
to be used on views we use instance variable something like @qasim

Active record and active relation

Active record, design pattern understand and interact with data

user = User.new #user an instance of User table
user.fn = "Qasim"
user.save # SQL insert

Active relation small queries combined together

  user = user.where(ln:"Qasim")
  users.each{|user|...}


  sub1 = Subject.find(2)
  sub1.update(:name=>"red", :position=>1)

  # Delete and Destroy
  # best to user Destroy

Condition methods "where"

Rails controller db commands

Take table Peopel

People.all list all value sin table people

Database association

one to many
many to many
many to one

CRUD

Controller Plural
model dealing g with singular

REST

transform state
Subject and pages cna have actions prospered on it
edit is transformation add is transformation
using CRUD as transformation
REST uses GET and POST HTTP verbs
PATCH update
DELETE detecting
RAILS resource full routes GET POST DELETE PATCH
- optimized for REST
- on routes.rb
- add resource:controller_name to get all the resourseful routes
- does not come with delete
```
    resources :pages do member
    do
    get :delete
    end
end

**```**
```

resourseful url helopers

Rails 2 Controller and view

Store data in cookies

HTML is stateless
we store dats in cvoockies or session
coookies work liske hash
set cookies[:username]="qasim" in conteller
acess @somevale = cookies[:username]
max 4kb
resided obn user compute r
use it to preserve state
dont store model, sesntive

Store data in sessions

similartr to cookies
server sends session ID -> saved in cookies
server uses that as session identifier
set session[:username]="qasim" in conteller
acess @somevale = session[:username]
Storage
- file system - slows
- session cookie can be intersepted
- suoer cookies - fast
  - encrypted and signed

Messaging with the flash hash(Viewed)

messge in persists for redirect and dispapers
perssists throughout session
flash[:notice] = "Log in successful"

Log information to a file

logs env info
can chose type of info to log
clear up log files rails log:clear
rake log:clear
use that wanywhere in ruby with back tick to clear up log file

Inherit common behaviors with ApplicationController

rails classes inherit behaviors from Application classes '<'
non method action should be kept private
use protecte in ApplicationController class to have subcalsses acess the method
secify wich action activates the filter
lets add proteccted confim logged in action

Use filters to call methods automatically

perform hosue keeping tasks
before and after controller action
check for login
3 ways to filter (private and protected )
- before_action
- after_action
- around_action

Understanding CSRF protections

add to applicationController ``
CROSS SITE forgery PROTECTION
form for adds csrf token automaically
for other use we can use <%= csrf_meta_tag %>

2. Rendering Views

Avoid double render errors

Render sets the tmeplate to be rendered
Redirect sets the value in http respose
use and return not &&
render (home_path) and return

Helper methods

text helper
- word_wrap : long text breaks it not lenth
  - <%= word_wrap(text, :line_wiedth=>30)%>
- simple_format : respect line break
- truncate: truncate(text, :length=>28) add 25 chars + ...
- pluralize ->
- truncate_work
- highlight
- excerpts
Sanatize helper
- prvent site break or CRS
- all contnet by user should be assumed unsafe
- could be melescisous
- html_escape(), h()
  - Rails 6 escape all html by default
  - unless you wan to allow it
  - can use the messafe.html_safe
  - strip_links(text) -> rmoves links from tag
  - or remo all html taqs
  - strip_tags(text)
number helper

number as first arg
hash of options
- :delimiter ' '
- :seprtor=> ','
- :precision => 2 (rounds it)
number to human size
number to phone

Date time helper

seconds, minutes, ....year
Time.now + 30.days - 23.minutes
Time.now - 30.days 30.dayago
Date time formating
`strftime'
Time.now.strftime('%B %d, %Y, %H:%M') -> June 12, 2020 13:23
or Time.now(format string

Form helpers
- form_tag(a,f) do end
- form_for (object, options) do |f| end
  - object can be used to retrive data from DB add and so on
  - f.text_field(:name)
- Select
Custom helpers
- all helpers are avaialable in all view template
- frequest codes
- ruby files ruby code

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ruby-and-ruby-on-rails-quick-start-guide's Introduction

Ruby - Quick - Guide

Sample Ruby react Application

documentation

Ruby Basics

Objects

variable

Numerics

String

Arrays

Hashes

Symbols

BOOLENA

Ranges

Constants

nil

Control Structure

if else if

unless

case

sortHand

loops

itirators

Best Practices

Exit a running script

Input and Output

Enumerable -> can be counted

code block 'do end'

find methods

Map/collec

inject/reduce methods

Sort <=> sapceship operator

merge methods

Ruby custom methods

Scope ...

retun value

return more than one vlue

---------------------------

Ruby Classes !!!1

---------------------------

Define calsses

attributes

Readed and Writer method

Attribaute methods

method acess calls

initialize methods

Challange

Class methods

class attributes

Class Reader Writer methods

Radio challange

Class inheritance

oversire and exrtend

Acess super calss from child class

DATE and TIME

Date class

Datetime class -> sub class of date time

Date time challange

Namespacing

Mixins

when to use what ? 4

Load Require and Include

challange

ECEPTIONS Begin Rescue End

Rails

creating controller and views

Routes

varibale vs instance variable (@)

Active record and active relation

Rails controller db commands

Database association

CRUD

REST

resourseful url helopers

Rails 2 Controller and view

Store data in cookies

Store data in sessions

Messaging with the flash hash(Viewed)

Log information to a file