javascript对haml中的ruby对象的评估抛出undefine方法异常

Question

I have a javascript that should change an haml element only when ruby object is define unfortunately the "#{project.builds.last.updated_at}" is been evaluated when the page is rendered ragrdeless to the if condition that is false, and therefore I am getting

"undefined method `updated_at' for nil:NilClass"

on project.build.last.

if ((#{@project.builds.size} && #{@project.builds.size}) > 0){  
  document.getElementById("lastSave").innerHTML = "#{@project.builds.last.updated_at}";
}

any idea how I can force the evaluation to be in real time?

Answer 1

You can use try method:

"#{@project.builds.last.try(:updated_at)}"

It will generate empty string if there are no builds , but it doesn't matter since this part of JS won't be executed under this condition. Though I would advice refactoring, cause inline JS with Ruby interpolations in HAML isn't very readable and easy to debug.