ALternative to eval for string-CodePudding

I have a string "Mymodel::FirstClass" stored in db and i need to call Mymodel::FirstClass (out from string). How to do this without using eval(string)?

CodePudding user response：

If you require Active Record, you can use constantize (see here)

So for example, something like this:

require "active_record"

"Mymodel::FirstClass".constantize
=> Mymodel::FirstClass

Or you can use const_get

Kernel.const_get("Mymodel::FirstClass")
=> MyModel::FirstClass

CodePudding user response：

You can use constantize as Stellenerger suggested. Or when the string might include a class names that might not exists then you might want to use safe_constantize which simply returns nil then the constant was not found instead of raising an exception:

"Mymodel::FirstClass".safe_constantize
#=> Mymodel::FirstClass

"NonExistingClass".safe_constantize
#=> nil