Rails 2 - expected Hash (got Array) for param

Question

So in HTML if I made a form like this:

<form method="post">
<input type="text" name="categories[][name]" />
<input type="text" name="categories[][name]" />
<input type="text" name="categories[][name]" />
<input type="text" name="categories[][name]" />
<input type="submit" value="submit" />
</form>

I expect params[:categories] to be

[{"name"=>"value"},{"name"=>"value"},{"name"=>"value"},{"name"=>"value"}]

But instead, rails 2 will raise a TypeError: expected Hash (got Array) for param

The error is raised here:

http://apidock.com/rails/Rack/Utils/normalize_params

Why is this not allowed or not parseable in rails? What am I missing?

I know I could index the input like so

<input type="text" name="categories[0][name]" />
<input type="text" name="categories[1][name]" />
<input type="text" name="categories[2][name]" />
<input type="text" name="categories[3][name]" />

And get a Hash. But this seems counter-productive.

Answer 1

You've got to reverse the subscript order:

<input type="text" name="categories[name][]" />