Question

I have a case where, either variable is defined, or variable is nil and alternative_variable is defined. I need to implement logic into interpolation to choose the variable among these that is defined. When I do:

some_value: "#{ variable || alternative_variable }"

when variable is defined, everything works fine. The moment variable is not defined (and alternative_variable is present), I get the following error:

undefined local variable or method `variable' for #<#Class:0x007fc3c021bc28>:0x007fc3c006c030>

I’ve found a way to bypass the error by adding the following code block before interpolation:

<% variable ||= alternative_variable %>

But it feels dirty and not-rails-way. Is there a neat and tidy way to place logic inside interpolation directly?

Answer 1

This has nothing to do with rails, it’s just ruby. Try this:

some_value: "#{ defined?(variable) ? variable : alternative_variable }"