Introduction

Hello everyone, this is Kota.
I use Rails in my daily work, and I would like to briefly share something I learned about hash keys that I handled the other day!

Trouble

What I did was obtain the data from the model, put the variable into it, and hashed the variable using the attributes method.
However, when accessing the hashed variable with user[:name] to obtain the value of name, nil was outputed and the value could not be obtained.

Investigation

As mentioned earlier, the return value when using the attributes method on the data obtained from the model was as follows. That's the time I noticed that the key is a string.

It is something obvious, but I realized again that the value can only be obtained by accessing it in the same format in which it is defined.

I was a little bit stuck from there because I often used symbols instead of strings to get the value of params, etc.

Further Research & Methodology

I took the opportunity to do a little more research on hash and compiled a list of methods that could be used when you are facing similar issues.

1. Convert key from string to symbol

• symbolize_keys

  • Methods provided by Rails. Internally, it uses ruby's transform_keys(&:to_sym) method.

• Reference: https://api.rubyonrails.org/classes/Hash.html#method-i-symbolize_keys

2. Convert key from symbol to string

• stringify_keys
  • Methods provided by Rails. Internally, it uses ruby's transform_keys(&:to_s) method.
• Reference: https://api.rubyonrails.org/classes/Hash.html#method-i-stringify_keys

3. If you also want to convert hash-nesting

One caveat to the above two methods is that if there are nests within the hash, they will not be converted.

If you want to convert nests as well, you can use deep_symbolize_keys (deep_stringify_keys) to do so.

PS:The method transform_keys of ruby is also deep_transform_keys, which can transform nests.

4. If you want to get both symbol & string

• with_indifferent_access

Check the class of the variable user that was used earlier.

Now let's change the class to ActiveSupport::HashWithIndifferentAccess using the method with_indifferent_access.

• Reference: https://api.rubyonrails.org/classes/ActiveSupport/HashWithIndifferentAccess.html

Try to get values in both strings and symbols.

Now you can retrieve the value as both a string and a symbol.
Params also extend this ActiveSupport::HashWithIndifferentAccess class and can retrieve values as both strings and symbols.

Summary

In this article, I briefly summarized the handling of hash keys and related methods used in Rails.
There are many useful methods related to hash, so please check them out yourself.

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