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Ruby Build a Todo List Application with Rails 4 Build a Todo List Application with Rails 4 Viewing Todo Lists

rigzin norboo
rigzin norboo
11,059 Points

Confused with scope :complete, -> { where("complete_at is not null") }

In incomplete scope it is clear that it will filter the rows from database that have complete_at: nil but in complete scope we are just passing string. How it is filtering the database.

1 Answer

Hi Rigzin,

The string is the database query; that's what gets passed into the query to deliver the required results. Using completed_at: nil is the Rails way of doing the same thing - Rails will convert completed_at: nil to a string such as "completed_ at is null" and query the database that way.

The two methods work the same way; one relies on Rails to generate the string, the other just uses the string directly. I would imagine that for more complicated queries, getting Rails to do the heavy lifting would make life easier, rather than trying to write the query directly.

I hope that helps,