Rails sort_by方法（如果值不为空）

Question

So I've got a method that I'm using to sort by the result instead of a database column at the moment which works nicely. It will return from the below each loop with a value against each record, then sort the table based on these:

<% @records.sort_by(&:methodName).reverse.each do |record| %>
    <%= record.methodName %>
<% end %>

This works really well - however this method only gets used after a user interacts with the record itself. For instance like a rating, so a record will begin life without a rating, then ratings will be submitted after this point.

It works nicely, until you create a new record that doesn't have a value for this to sort by - is there a way of saying "Sort by what this method returns, if the record doesn't have a value for this, put it at the bottom"?

At the moment I get an exception because it's not a number 'NaN'...because it's empty :(

As always - any help massively appreciated for a Rails beginner here..!

Answer 1

Try this

<% @records.sort_by{|r| r.try(:methodName)}.reverse.each do |record| %>

Edit:

<% @records.sort_by{|r| r.methodName.nan? ? 10000 : r.methodName}.reverse.each do |record| %>

Answer 2

Assuming that methodName always exists (as a method) and returns a Numeric when the value exists and nil or false otherwise:

@records.sort_by{ |r| r.methodName || -9999999 }

That will cause all records with no entry to be at the start of the list before the reverse , and at the end of the list afterwards.

If that doesn't work, please state what methodName returns for the new records.

Alternatively, you could do this:

newrs, oldrs = @records.partition{ |r| r.methodName }
newrs.each do |r| ... records that have a value for methodName ... end
oldrs.each do |r| ... records with no value for methodName ... end