What does the ||= operator mean in ruby?

Question

ruby

Unfortunately, I couldn't find the answer on ruby-doc.org and on the first pages of google.
Found in this context:

def permitted_params
            @permitted_params ||= declared(params, 
               include_missing: false)
end

Answer 1

In this case, ||= means that if the variable @permitted_params is not assigned a value, i.e. it is equal to nil or false, then you need to assign declared(params, include_missing: false) to it, therefore @permitted_params = declared(params, include_missing: false).
Otherwise, if it has a value, nothing needs to be done.