[Ruby] How to convert from lowercase to uppercase and from uppercase to lowercase

Overview

I used the ** downcase ** method in my Rails tutorial. I haven't had a chance to use it before, so I would like to deepen my understanding while solving the problem this time. I would also like to take a brief look at related methods.

--Related methods

--Methods used in the following problems - start_with? - end_with?

--Practice --Problem --Answer --Another solution

--Summary

--References

Related methods

Method	How to use
downcase	Convert uppercase to lowercase
upcase	Convert lowercase letters to uppercase
swapcase	Convert uppercase to lowercase and lowercase to uppercase
capitalize	Convert first lowercase letters to uppercase
Destructive method(!)	At the end of the above method( ! )When you giveobjectMake changes to

Method used in the following problem

start_with?

A method to check if it starts with the specified string

end_with?

A method to check if it ends with the specified string

Practice

problem

There are any two strings. Write a program that compares strings and checks if the other string is included at the end of the string.

answer

I'm using downcase because I don't want to distinguish between lowercase and uppercase. It works fine with all uppercase letters using the upcase method.

def end_other(a, b)

  #Convert to lowercase and store in variable
  a_down = a.downcase 
  b_down = b.downcase

  #The character string of b is included in the character string of a?Or is the string a in the string b?
  if a_down.end_with?(b_down) || b_down.end_with?(a_down)
    p 'True'
  else
    p 'False'
  end
end

#Method call
end_other('Apple', 'Ple')
end_other('orange', 'Range')
end_other('banana', 'Nana')

Another solution

By using slice, the part specified by the argument is cut out. For slice, please refer to here.

def end_other(a, b)

  #Convert to lowercase and store in variable
  a_down = a.downcase
  b_down = b.downcase

  #Get the length of a string
  a_len = a_down.length
  b_len = b_down.length

  #Cut the character of the character string of a from the character string of b and equal to the character string of a.?Or, cut the character of the character string of b from the character string of a and equal to the character string of a.?
  if b_down.slice(-(a_len)..-1) == a_down || a_down.slice(-(b_len)..-1) == b_down
    p 'True'
  else
    p 'False'
  end
end

#Method call
end_other('Apple', 'Ple')
end_other('orange', 'Range')
end_other('banana', 'Nana')