how does a template know to use attributes before type cast after a validation error

rubyonrails-talk
1

I wonder if anyone could help me with this.

In normal circumstances, re-rendering a form fields with validation errors, show original entered data and not type_cast data from the object.

However, I have a situation where I am submitting a number of values to do a bulk update. My model converts the returned values and does the necessary processing, building the data structure from the request params hash.

However, when I use this to re-display the form using render :action, the values I get are the ones after type_cast. ie. 'x' entered for numeric becomes 0

I know from my unit tests that the model has built my object with the correct associations, and the objects with validation errors are still shown as new_record and the attribute_before_validation is there as entered by the user.

So I am wondering what Rails uses to determine how to redisplay the fields (I had assumed that it checked for new_record and used attribute_before_validation). But this does not seem to be the case

I can only think that it is done from the params hash. Now in my case, the input fields do not follow the conventional object name derivation, but the naming would be consistent with the params hash.

The only reason I can come up with at the moment for the post validation values being shown is that Rails does some sort of cross reference between the input field name values, the params hash and the object values. Which I have made not consistent

Any ideas?

Thanks Tonypm

2

OK - I have my answer.

Rails helpers can only get at the object's attribute_before_validation, if the helper has the object passed to it.

In my case, I was using text_field_tag which of course gets the value and not the object. It was staring me in the face really.

So in my case, I can use the text_field with model, attribute symbols, and set the name to be whatever I want. And that works.

Silly me!

Tonypm