[Ruby] present/blank method and postfix if.

This is a personal memo.

By using the if statement and the present? Or blank? Methods, the process can be branched depending on whether the value is set in the variable.

In ruby, if can be written after (called postfix if). You can use this to make a simple description.

present? and blank?

Object.present? Returns true if object has a value.

Object.blank? Returns true if object has no value or is empty. There is no value for nil and empty ("").

If there is no value

irb(main):333:0> x
=> nil

irb(main):333:0> x.present?
=> false

irb(main):334:0> x.blank?
=> true

If there is a value

irb(main):335:0> test
=> "test"

irb(main):336:0> test.present?
=> true
irb(main):337:0> test.blank?
=> false


There are also nil? And empty? Methods that are similar to blank ?. The relationship between the object to be verified and the output is as follows.

Method nil empty ("")
blank? true true
nil? true false
empty false true
present? false false

If the value is empty

irb(main):340:0> z = ""
=> ""
irb(main):341:0> z.empty?
=> true
irb(main):342:0> z.nil?
=> false

## Postfix if Apply a conditional expression after the process. Line breaks and end in the conventional description can be omitted.

Processing if conditional expression

Postfix if

def jadge(x)
  "exist" if x.present?

Normal if statement

def jadge(x)
  if x.present?

## Conditional bifurcation depending on the presence or absence of a variable value Conditional bifurcation is possible by using blank or present. You can write it clearly by using the postfix if.


def jadge(x)
  y = "No" if x.blank?
  y = "Exist" if x.present?
  p "the answer#{y}is"

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