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Ruby: How to convert a string to uppercase?

Ruby: How to convert a string to uppercase?

How to convert a string to uppercase in Ruby?

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Alexandre Calaça
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Table of contents

Greetings

Hey, It's AC (Alexandre Calaça) here. Hope you're good. Let's get down to business. Shall we?

Introduction

Today, let's learn and practice how to convert a string to uppercase in Ruby.

Solution

In Ruby, the upcase method is used to convert a string to uppercase.

The upcase method is immutable, it means it returns a copy of self (current object) with all characters uppercased, so, just to be clear, the original string stays the same.

The mutable version is used with a bang sign at the end, upcase!

Syntax

"my_string".upcase

In this case, my_string is the string we are interested to uppercase.

Parameters

The upcase method doesn't require any parameters.

Return value

Since it is an immutable method, it returns a new uppercased string of the caller. If no conversion is necessary, it returns the unchanged original string.

Again, it's possible to return and modify self (current caller) if we use the bang operator after the method: upcase!.

Coding time

Let's go over the examples.

irb(main):001:0> my_string = "alexandre"
irb(main):002:0> my_string.upcase
=> "ALEXANDRE"
irb(main):003:0> my_string
=> "alexandre"

In the previous examples, it's noticeable that:

  • The upcase method doesn't modify the original string;
  • It returns a new uppercased string of the caller;
irb(main):006:0> my_new_string = "ALEXANDRE CALACA"
irb(main):007:0> my_new_string.upcase
=> "ALEXANDRE CALACA"

it's possible to see that:

  • The upcase method returns the same string if no conversion is necessary.
> my_string = "AlExAnDRe CalACa"
=> "AlExAnDRe CalACa" 
> my_string.upcase
=> "ALEXANDRE CALACA" 
> my_string
=> "ALEXANDRE CALACA"

The bang operator allows the upcase method to modify self.

Errors

  • NoMethodError
    If the method is not used with a String object
2.7.3 :026 > array.upcase
NoMethodError (undefined method `upcase' for [1, 2, 3]:Array)
2.7.3 :027 > 4.upcase
NoMethodError (undefined method `upcase' for 4:Integer)
  • ArgumentError
    If it's provided unnecessary arguments.
2.7.3 :028 > my_string
 => "ALEXANDRE CALACA" 
2.7.3 :029 > my_string.upcase("test")
ArgumentError (invalid option)

Conclusion

In this article, it was possible to learn and practice how to convert a string to uppercase in Ruby. There are excellent examples.

That's all for today. Reach me out if you have any questions, guys.

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