Menu
<% if dashboard_pane_counter.remainder(3) == 0 %> do something <% end> If dasboard_pane_counter wasn't defined, how can I get this to evaluate to false rather than throw an exception?
240
Use the typeof operator to check if a variable is defined or initialized, e.g. if (typeof a !== 'undefined') {} . If the the typeof operator doesn't return a string of "undefined" , then the variable is defined.
@title is an instance variable - and is available to all methods within the class. In Ruby on Rails - declaring your variables in your controller as instance variables ( @title ) makes them available to your view.
Ruby Class VariablesClass variables begin with @@ and must be initialized before they can be used in method definitions. Referencing an uninitialized class variable produces an error. Class variables are shared among descendants of the class or module in which the class variables are defined.
<% if defined?(:dashboard_pane_counter) && dashboard_pane_counter.remainder(3) == 0 %> # do_something here, this assumes that dashboard_pane_counter is defined, but not nil <% end %> When using rails and instance variables, nil has a try method defined, so you can do:
<% if @dashboard_pane_counter.try(:remainder(3)) == 0 %> #do something <% end %> so if the instance variable is not defined, try(:anything) will return nil and therefore evaluate to false. And nil == 0 is false
43
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
