optional local variables in rails partial templates: how do I get out of the (defined? foo) mess?

Question

I\'ve been a bad kid and used the following syntax in my partial templates to set default values for local variables if a value wasn\'t explicitly defined in the :locals has

Answer 1

This is a derivative of Pablo's answer. This allows me to set a default ('full'), and in the end, 'mode' is set in both local_assigns and an actual local variable.

haml/slim:

- mode ||= local_assigns[:mode] = local_assigns.fetch(:mode, 'full')

erb:

<% mode ||= local_assigns[:mode] = local_assigns.fetch(:mode, 'full') %>

Answer 2

How about

<% foo ||= default_value %>

This says "use foo if it is not nil or true. Otherwise assign default_value to foo"

Answer 3

In my case, I use:

<% variable ||= "" %>

in my partial.
I don't have idea if that is good but for my is OK

Answer 4

I do this:

<% some_local = default_value if local_assigns[:some_local].nil? %>

Answer 5

I think a better option that allows for multiple default variables:

<% options = local_assigns.reverse_merge(:include_css => true, :include_js => true) %>
<%= include_stylesheets :national_header_css if options[:include_css] %>
<%= include_javascripts :national_header_js if options[:include_js] %>

Answer 6

If you do not want to pass local variable to partial each time you call it you do this:

<% local_param = defined?(local_param) ? local_param : nil %>

This way you avoid undefined variable error. This will allow you to call your partial with/without local variables.