[Ruby] How to write blocks


Since I learned about blocks to deepen my understanding of Ruby, I will output it.

What is a block?

--do ~ end is called a block in Ruby.

For example, such a problem because it is easier to understand if there is an example. (There are other ways to solve it, but this time the times sentence) ** A block is an argument of the times method. It is repeated by writing in do ~ end so that iterative processing is performed according to the contents of the block. ** **

[Problem] Add the numbers from 1 to 10 in order, and output the result of adding all at the end to the terminal.

sum = 0

10.times do |i|
  sum += i + 1

puts sum

#Terminal output result
# 55

How to write a block

In the above problem, I used do ~ end. There are other ways to write blocks. For example, it looks like this.

sum = 0
10.times { |i| sum += i + 1 }

puts sum

#Terminal output result
# 55

By enclosing do ~ end with{}, Ruby recognizes it as a block.

Each person has their own way of writing, but keep in mind that there is such a way of writing. It seems that {} is used when it fits in one line, and do ~ end is used for long code including line breaks.


A program that calls and outputs normal methods

The normal method is called and puts is output.

##Normal calling
def normal
  puts 'nomal method call'


#Terminal output result
#nomal method call

Execute block using yield

The block (do ~ end) passed to the nomal method is called.

##Call the block passed when calling the nomal method with yield
def normal
  puts 'nomal method call'

normal do
  puts 'Call with yield'

#Terminal output result
#nomal method call
#Call with yield


Add an argument to yield

By putting an argument in yield when calling the block, any thing (argument value) is passed to the block.

def normal
  puts 'nomal method call'
  yield('Give an argument')

#The argument is passed to the block by giving an argument to yield
normal do |text|
  puts text

#Terminal output result
#nomal method call
#Give an argument

Explicitly described

point --nomal (& block argument) --Block argument .call (argument you want to pass to the block)

def normal(&block) #In the argument block&Put on
  puts "nomal method call"
  block.call("Give an argument") #Block with call method(block)Run

normal do |text|
  puts text


--There are "do ~ end" and "{}" in the block. ――You can write clearly by using "{}". --Use "{}" if it fits on one line, and "do ~ end" if you need a line break. You can execute the block passed to the method by using --yield. --~~ If you want to execute the block explicitly, add & before the argument. ~~ --~~ The block received as an argument can be called with the "call method". ~~ --In order to receive the block as a Proc object, add & before the argument. --Use the call method to receive and execute the block.


-Ruby 2.7.0 Reference Manual -[Block? yield? ] A solid understanding of Ruby's Proc objects

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