[Ruby] Various types of each

Introduction

As I was studying, various kinds of each came out. I will write it so as not to forget it. : sunny:

each method

1. Methods provided for arrays and range objects. Extracts the elements contained in the object.

fruits = [ "apple", "orange","banana"]
 
fruits.each do |fruit|
  p fruit
end

#=>"apple"
#  "orange"
#  "banana"

2. If you want to retrieve and use the key and value of the array at the same time, set two variables.

fruits = { apple: 100, orange: 200, banana: 300}

fruits.each do |key, value|
  puts "#{key}The price of#{value}It is a circle."
end

#=>"The price of apple is 100 yen."
#  "The price of orange is 200 yen."
#  "The price of banana is 300 yen."

It can also be described as follows. (If you like. When writing a long block, write ⇧ like before, if you want to write compactly, ⇩)

fruits = { apple: 100, orange: 200, banana: 300}

fruits.each { |key, value| puts "#{key}The price of#{value}It is a circle."}

#=>"The price of apple is 100 yen."
#  "The price of orange is 200 yen."
#  "The price of banana is 300 yen."

each_key method

It is used when you want to retrieve only the key.

fruits = { apple: 100, orange: 200, banana: 300}

fruits.each_key {|key|  p "#{key}Price" }

#=>"Apple price"
#  "Price of orange"
#  "banana price"

each_value method

It is used when you want to retrieve only value.

fruits = { apple: 100, orange: 200, banana: 300}

fruits.each_value { |value| p "#{value}Circle"}

#=>"100 yen"
#  "200 yen"
#  "300 yen"

each_with_index method

1. Use this when you want to use index numbers other than array elements.

fruits = [ "apple", "orange","banana"]
 
fruits.each_with_index do |a,i|
  p "#{i}Of#{a}there is."
end

#=>"There are 0 apples."
#  "There is one orange."
#  "There are two bananas."

2. You can specify a numerical value to start by setting the initial value of index in the argument. (When you want to start from number ◯.)

fruits = [ "apple", "orange","banana"]
 
fruits.each.with_index(5) do |a,i|
  p "#{i}Of#{a}there is."
end

#=>"There are 5 apples."
#  "There are 6 oranges."
#  "There are 7 bananas."

each_slice method

Specify the number in the argument. By doing so, you can slice the specified number as the name suggests and retrieve the element.

fruits = [ "apple", "orange", "banana", "lemon","lime"]

fruits.each_slice(2) do |fruit|
  p fruit
end

#=>["apple", "orange"]
#  ["banana", "lemon"]
#  ["lime"]

each_line method

It can be taken out separately at the line break.

fruits = "apple\norange\nbanana\nlemon"
fruits.each_line {|line| p line.chomp }

#=>[:apple, :orange, :banana, :lemon]

each_with_object method

Evaluates the object and element of the argument and finally returns the object of the argument.

arr = [1, 2, 3]

result = arr.each_with_object({}) do |item, memo|
  memo[item] = item + 1
end

p result
#=>{1=>2, 2=>3, 3=>4}

`This is further as Fukahori. .. ``

-What is the difference between inject and each_with_object?

Summary

I found that there are various types of friends in each. Let's expand the range that can be remembered little by little ...! !! : fire: