Regarding form_for and fields-for content variable

rubyonrails-talk
1

I am trying to understand what I am working with when I deal with Rails forms_for and fields_for constructors.

Given model has_many associations belongs_to dependency and           dependency has_many associations belongs_to model

@model = Model.find(:id)

and

forms_for @model do |f|

what is 'f'?

   f.fields_for :associations do |ff|

what is 'ff'?

How do I access dependencies on the named associations?

I have inspected these things and the volume of data that each contains is such that I cannot post it here. My difficulty is that I cannot seem to get a handled

I will try to give an example:

forms_for @model do |f|

   f.fields-for :associations do |ff|

   ff.text-field :model_id    ff.text_field :dependency_id:

   ff.dependency.some_attribute # this display value simply does not work.

   ff.collection_select(                   :dependency_id, @dependencies, :id, :name,                   { :prompt => 'Select a name' }, #options hash                   { :class => :input_select, #html hash                     :id => :input_name,                     :size => 1,                     :title => I18n.t('Enter a valid name'),                     :value => ff.dependency_id } # this does not work either                   )

Now, while I know that ff != dependency it does seem to me counter intuitive that for each association of model I am unable to directly address the dependency attributes from within the form constructor.

What is my fundamental misunderstanding with respect to forms_for and fields_for and their treatment of DBMS rows? How does one obtain a dependent attribute for display purposes within a forms_for or fields_for construct?

2

This should be association rather than dependency. What I am asking is why, when ff acts in the place of a specific model.association, I cannot reach model.association.dependency.attribute.

The problem domain requires that associations be created separately from either the model or the dependency but must be associated to an extant qualified row in each.

3

James Byrne wrote:

I am trying to understand what I am working with when I deal with Rails forms_for and fields_for constructors.

Given model has_many associations belongs_to dependency and           dependency has_many associations belongs_to model

@model = Model.find(:id)

and

forms_for @model do |f|

what is 'f'?

A FormBuilder. The documentation for form_for already tells you this.

Best,

4

The most general it is a block value. For a from builder |f| is a form object with association parameters that have attributes that correspond to the object. f.text_field :name, :name is a db column or an attribute of the class.

same as: array.each do |val|   puts val end