(Determine in 1 minute) About the proper use of empty ?, blank? And present?

(Note) Explanation I have summarized it so that it can be used immediately with the minimum explanation. (Conclusion) If you remember either blank? Or prresent ?, you can do something about it.

When using empty?

** Used when you want to know if the contents are empty after satisfying the following conditions. ** ** ① There must be a container ② The contents are not numbers or true or false

  if box.empty?

If ①② is not satisfied, NoMethodError will occur.

When using blank?

** Used when you want to know if the contents are empty or exist in the first place **

 irb(main):001:0> box = nil
=> nil
irb(main):002:0> box.blank?
=> true

When using present?

** Used when you want to know that it exists and the contents are not empty (synonymous with! Blank?) **

irb(main):006:0> box = nil
=> nil
irb(main):007:0> box.present?
=> false

I want to know a little more, what should I do in this case? When


It was easy to understand because it covers the patterns in a tabular format.

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