nested attributes ids arrays syntax problem

Question

So, there is a working part of code in rails 5. I'm making huge form with nested attributes on many levels. I've got an strong params list:

params.require(:lexeme).permit(
    :word, :homonym_number, :see_other_lexeme_id, :semantic_description, :afterword,
    variants_attributes: [ :word, :id, :_destroy, proofs_attributes: [ :word, :language_id, :meaning, :id, :_destroy, language_mode_ids: [] ] ]
  )

And when I tried to change order a little bit...

params.require(:lexeme).permit(
    :word, :homonym_number, :see_other_lexeme_id, :semantic_description, :afterword,
    variants_attributes: [ :word, :id, :_destroy, proofs_attributes: [ :word, :language_id, :meaning, :id, language_mode_ids: [], :_destroy ] ]
  )

I'm getting:

syntax error, unexpected ']', expecting =>
...guage_mode_ids: [], :_destroy ] ]
...                              ^):

So, rails masters, what is wrong with this simple syntax here, has always array parameters need to be placed as last? What if I have more arrays in params?

engineersmnky · Accepted Answer · 2019-05-31 19:12:24Z

1

The problem is that the last :_destroy should be a key => value according to the syntax sugar lexical parsing.

If you want to retain the new order you need to make language_mode_ids: [] a literal Hash like so:

params.require(:lexeme).permit(
  :word, :homonym_number, :see_other_lexeme_id, :semantic_description, :afterword,
  variants_attributes: [ :word, :id, :_destroy, 
    proofs_attributes: [ 
      :word, :language_id, :meaning, :id, {language_mode_ids: []}, :_destroy 
    ] 
  ]
)

Ruby is trying to help you by allowing you to specify language_mode_ids: [] but it will require all the arguments on the right hand side of that to also represent a key value pair.

Since :_destroy is just a symbol the interpreter does not know what to do with this. That is why your first order worked and the new order does not.

edited May 31, 2019 at 19:12

answered May 31, 2019 at 18:59

engineersmnky

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1 Comment

blazpie Over a year ago

thanks for clarifying. Sometimes syntax helpers could be confusing.

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