Blocks in Ruby

Blocks in Ruby

def get_items_from_api(page=0, page_size=10)
  start = page * page_size
  entire_list = (1..30).to_a
  slice_of_list = entire_list.slice(start, page_size)

  slice_of_list
end


def run_0
  page = 0
  loop do
    paginated_list = get_items_from_api(page)  
    break if paginated_list.empty?     
    
    puts "Working with this array: #{paginated_list}"    
    paginated_list.each do |item|
      puts "Working with this item: #{item}"
    end    
    
    page +=1    
  end
end



# this method accepts a block that loops through an enumerable
def looper(&heaven)
  return unless block_given?

  page = 0
  page_size = 10
  loop do  
    paginated_list = get_items_from_api(page, page_size)
    break if paginated_list.empty?
    
    heaven.call(paginated_list)      # yield(paginated_list)
    
    page += 1
  end
end

def run_0
  page = 0
  loop do
    paginated_list = get_items_from_api(page)  
    break if paginated_list.empty?     
    
    puts "Working with this array: #{paginated_list}"    
    paginated_list.each do |item|
      puts "Working with this item: #{item}"
    end    
    
    page +=1    
  end
end



def run_1
  looper do |items|
    puts "working with this set of items: #{items}"
  end   
end



def run_2
  looper{|items| puts "another way to work with: #{items}"
end



############ FILES

begin
  file = File.open(file_name, "w")
  file.write("your text") 
rescue IOError => e
  #some error occur, dir not writable etc.
ensure
  file.close unless file.nil?
end


File.open(file_name, 'w') do |f|
  f.write "writing line to file!"
rescue IOError
  #handle error
end


def my_method(f)
  f.write("write this!")
rescue IOError
  # handle some how
end


File.open(file_name, 'w', &my_method)



######################## Transactions

def transfer_money
 
  ActiveRecord::Base.transaction do
    john.update!(money: john.money + 100)
    ted.update!(money: ted.money - 100)
  rescue SpecialError => e
    # handle in a way
  rescue ActiveRecord::NotFound
    # notify devs
  end
 
end


######################### Tap

def make_a_user
  u = User.new
  u.build_profile
  u.store_avatar
  u.send_email_confirmation
  u.any_other_setup_required_when_creating_a_new_user
  return u
end



def make_a_user_2
  User.new.tap do |u|
    u.build_profile
    u.store_avatar
    u.send_email_confirmation
    u.any_other_setup_required_when_creating_a_new_user
  end
end


u = User.new(args).tap(:&save)


u = User.new(args)
u.save
return u


User.where(name: "Steve").yield_self do |scope|
  if quentin_is_awesome?
    scope.sort(:awesome)
  else
    scope.sort(:id)
  end
end.where(state: 'RI')



a = [
  User.where(name: "Steve"),
  if quentin_is_awesome?
    User.sort(:awesome)
  else
    User.sort(:id)
  end,
  User.where(state: "RI")
].compact.reduce(:&merge)




#Debugging chaining methods

query = User.where(status: "active").where(first_name: "John").where(state: "MD")

query = User.where(status: "active")
puts "status - #{query.count}"
query = query.where(first_name: "Jonathan")
puts "first_name - #{query.count}"
query = query.where(state: "MD")
puts "state - #{query.count}"


u.where(status:     "active").tap{|q| puts "active count: #{q.count}"}.
  where(state:      "first").tap{|q| puts "state count: #{q.count}"}
  where(first_name: "John" ).tap{|q| puts "first_name count: #{q.count}"}.