So far, this chapter has shown you how to use a number of the helper methods that come with Rails. You can also create your own helper methods. There are lots of good reasons to do so:

Creating helper methods might not be your very first priority in creating an application, but once you have a basic idea of what you want to create in your views, it’s a good idea to start assembling common tasks into helper methods.

Within the application directory structure, helper methods go into the app/helpers directory. At this point, the guestbook application will have two files there: application_helper.rb and people_helper.rb. Helper methods that are defined in application_helper.rb are available to views throughout the entire Rails application, whereas methods defined in people_helper.rb are only available to views that pertain to operations on the person model. For now, the helper methods built in this section can go in people_helper.rb and graduate to application_helper.rb if you think they’re worth sharing across the application.

The first helper method will take the Example 6-4 code for generating radio buttons from a hash. Example 6-6 shows what’s left when this is reduced to a call to the buttons helper method.

<% nations = { 'United States of America' => 'USA', 'Canada' => 'Canada', 'Mexico'
=> 'Mexico', 'United Kingdom' => 'UK' }%>

  <p>
    <b>Country</b><br />
    <%= buttons(:person, nations) %>
  </p>

The buttons method is in the people_helper.rb file, the contents of which are shown in Example 6-7.

1   module PeopleHelper
2
3   def buttons(model_name, target_property, button_source)
4       html=''
5       list = button_source.sort
6       list.each do|x|
7         html << radio_button(model_name, target_property, x[1])
8         html << h(x[0])
9         html << '<br />'
10     end
11     return html
12  end
13
14  end

There’s a lot going on in the buttons method. It’s contained by the PeopleHelper module, which was originally empty in the version created by the scaffolding. Lines 2 through 13 are all new additions. This version of buttons, defined starting on line 3, looks more like the older version of the helper functions, taking a model name as its first argument, then the targeted property, and then the source from which the radio buttons will be created.

Because the helper function isn’t in the view, there isn’t any ERb markup here. Instead, the helper function builds a string, starting in line 4. Often, the first declaration of the string includes the first tag, but as the radio buttons don’t have a containing element, this starts with the empty string. Lines 5 and 6 are the same logic for sorting the hash as was used in the original code from Example 6-3, but the contents of the loop, in lines 7 to 9, are very different.

Lines 7 through 9 all append something to the html variable, using the << operator. Line 7 appends radio button markup created through Rails’ radio_button helper. Line 8 appends the text the user will see, and line 9 appends a <br /> tag, putting a line break between the buttons. Rails developers often avoid mixing explicit markup with code, preferring to use content_tag or other helper methods—but you can use markup here if you think it’s appropriate.

Line 10 just closes the loop over the hash, but line 11 is a bit unusual. Explicit return statements aren’t necessary in Ruby methods unless you’re returning multiple results or want to break at an unexpected time. Ruby will assume that the last variable you touched is the return value. However, using return is a good way to avoid surprises, and if you feel like writing briefer code, you can leave off return and just write html there.

If you leave off line 11 completely, however, you’ll have an unpleasant surprise, shown in Figure 6-6. It looks like html was the last variable touched in line 9, but the each loop block, which closes in line 10, is actually considered the last thing touched. The value of the block is the underlying array, which gets mashed together to yield this unfortunate result.

Figure 6-6. Instead of radio buttons, an unpleasant squashed list

def button_select(model_name, target_property, button_source)
    html=''
    list = button_source.sort 
    if list.length <4
      list.each {|x|
       html << radio_button(model_name, target_property, x[1])
       html << h(x[0])
       html << '<br />'
      }
    else
       html << select(model_name, target_property, list)
    end

    return html
    end
end

def button_select(model_name, target_property, button_source)
     list = button_source.sort
     if list.length < 4
       list.collect do |item|
          radio_button(model_name, target_property, item[1]) +  
h(item[0])
       end.join('<br />')
     else
       select(model_name, target_property, list)
     end
end