Reference This is a memo for myself when I didn't understand the hash of ruby. If you make a mistake, please comment.

environment

ruby 2.7.1

Definition

Can be defined by all of the following

Thank you for your correction comment. "


#String and=>
hash1={"first"=>"Ichi"}

#With symbols=>
hash2={:first=>"Ichi"}

#Omitted writing when the key is a symbol
#(:"first"→:You can create the symbol first)
hash3={"first":"Ichi"}

Omitted writing when the key is a symbol
hash4={first:"Ichi"}

Of course this is not possible

#With symbols:
hash5={:first:"Ichi"}
=>syntax error

The contents are different

--hash1 → String is the key --hash2,3,4 → Symbol is the key

#hash1
{"first"=>"Ichi"}

#hash2,3,4
 {:first=>"Ichi"}

When calling


hash1["first"]
hash2[:first] #hash2,3,4 common

appendix

If you're not careful, you might make a mistake


hoge="second"
hash5={hoge:2,hoge=>2}
hash5
=> {:hoge=>2, "second"=>2}

You can also do this


hash={"first"=>1,:first=>"Ichi"}

Ruby Hash notes