[Ruby] Arguments with keywords and default values of arguments

Introduction

version ruby 2.6.3 rails 5.2.3

I was addicted to it because I didn't really understand the arguments with keywords. Even though I used equal to define a method with a default value, I was calling an argument with a keyword when calling the method, so an unintended argument was passed and an error occurred. It was.

This mistake

#Define methods with default valued arguments
def hello(lang = "ja", place = "Japan")
 puts "#{lang} : #{place}"
end

#How to call arguments with keywords
hello(lang: "en", place: "America")
#=>
{:lang=>"en", :place=>"America"} : Japan

The argument was interpreted as a hash and an unintended argument was passed.


About arguments with keywords

Reference https://qiita.com/jnchito/items/74e0930c54df90f9704c

def hello(lang: "ja", place: "Japan")
 puts "#{lang} : #{place}"
end

#Call with no arguments
hello
#=>
ja : Japan

#Call by changing the argument value with keywords
hello(lang: "en", place: "America")
#=>
en : America

#Call with non-keyword arguments
hello("en", "America")
#=>
wrong number of arguments (given 2, expected 0) 

Calling a method with keyworded arguments without arguments calls the method with default values. An error occurs if you try to call it with a keywordless argument.

About arguments with default values

Reference https://rooter.jp/programming/ruby_method_default/

def hello(lang = "ja", place = "Japan")
 puts "#{lang} : #{place}"
end

#Call with no arguments
hello
#=>
"ja : Japan"

#Call with non-keyword arguments
hello("en", "America")
#=>
en : America

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