FormHelper vs. FormTagHelper Methods

Use FormHelper methods when you are using a form to edit a row in a database, or to add a new row to the database.
Use FormTagHelper methods when the piece of data you are inputing does not directly correspond to any field in the database.
References:

api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html
api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html

Form

FormTagHelper Version:

<% form_tag 'show' do %>
... Controls go here.
<% end %>

FormHelper Version:

<% form_for @item, url: convert_show_path do |f| %>
... Controls go here.
<% end %>

Textfield

FormTagHelper Version:
```
<%= text_field_tag :celsius, '20', class: 'tf' %>
```
:celsius is the name; '20' is the initial value.

FormHelper Version:
```
<%= f.text_field :celsius, class: 'tf' %>
```
:celsius is the field of the database object f.
Dropdown Menu

FormTagHelper Version 1:
```
<%= select_tag :source_rate,
      options_for_select(
         [['Dollars', 1.00000],
          ['Euro', 1.36749],
          ['Pesos', 12.6149],
          ['Pounds', 1.58228]]),
      class: 'ddm' %>
```
:source_rate is the name; the first column of the array are the values displayed in the dropdown menu; the second column are the values returned to the controller to be read by a params statement. The option tags are the HTML option tags.

FormTagHelper Version 2:
```
<%= select_tag :source_rate,
      options_from_collection_for_select(
          @exchange_rates, :curr_name, :rate),
      class: 'ddm' %>
```
:source_rate is the name; the options_from_collection_for_select method takes three arguments:
    (1) @exchange_rates: the collection containing the information for the dropdown menu,
    (2) :curr_rate: the field value to send to the server to be read in the params array,
    (3) :curr_name: the field to display in the dropdown menu.

FormHelper Version:
```
<%= f.select :source_rate, 
     [['Dollars', 1.00000],
      ['Euro', 1.36749],
      ['Pesos', 12.6149],
      ['Pounds', 1.58228]],
     class: 'ddm' %>
```
:source_rate is the field of the database object f; the values of the dropdown menu are specified in the array as they were in the FormTagHelper version. Note that for the FormHelper version, no options_for_select method is needed.
Radio Button

FormTagHelper Version:
```
<%= radio_button_tag :group, value, true %>
```
:group sets the button group (in a group of radio buttons, only can be checked at a time)
:value is the value returned to the controller to be read by a params statement
true means that the radio button should be initially checked.

FormHelper Version:
```
<%= f.radio_button :group, value, checked: true %>
```
:group sets the button group (in a group of radio buttons, only can be checked at a time)
value is the value returned to the controller to be read by a params statement
checked: true means that the radio button should be initially checked.
CheckBox

FormTagHelper Version:
```
<%= check_box_tag :sugar, 1, true, class: 'cb' %>
```
:sugar is the name of the checkbox
1 is the value returned to the controller in a params statement
false means that the checkbox is initially checked.

FormHelper Version:
```
<%= f.check_box :sugar, 1, checked: true, class: 'cb' %>
```
:sugar is the name of the checkbox
1 is the value returned to the controller in a params statement, 0 is returned if the box is not checked.
checked: true means that the checkbox is initially checked.