map_by_method now works with ActiveRecord associations

map_by_method now works with ActiveRecord associations

Posted by Dr Nic on August 12, 2007

I was always annoyed that map_by_method was broken for ActiveRecord has_many associations. 6 mths later I finally fixed it.

That’s the magic of Open Source Software. [/end sarcasm]

So now, the following example works like it should:

$ gem install map_by_method $ console > require 'map_by_method'  # stick this in your environment.rb for Rails > user = User.find_by_name "Dr Nic" > user.companies.map_by_name => ['Dr Nic Academy', 'Dr Nic Institute of Being Silly'] > user.companies.map_by_id_and_name => [[1, 'Dr Nic Academy'], [9, 'Dr Nic Institute of Being Silly']] 

Recap: why use map_by_method?

Try the following example:

> user.companies.map_by_employees.flatten => list of all employees of user 

Versus:

> user.companies.map { |company| company.employees}.flatten or > user.companies.map(&:employees).flatten 

Or compare:

> user.companies.map_by_id_and_name => [[1, 'Dr Nic Academy'], [9, 'Dr Nic Institute of Being Silly']] 

Versus:

> user.companies.map { |company| [company.id, company.name]} 

That is, it looks and feels just like ActiveRecord’s #find method, with its find_by_first_name_and_last_name magic.

Summary

No {, }, |, &, or : required. Just clean method names.

Bonus other gem

In the spirit of ActiveRecord hacks, there is to_activerecord:

$ gem install to_activerecord $ console > require 'to_activerecord'  # stick this in your environment.rb for Rails > [1,2,3].to_user => [list of User with id's 1,2,3] 

To me, this suffix operator reads cleaner than the traditional:

> User.find([1,2,3]) 

For example, if you want to perform an operation on the list of Users:

> ids = [1,2,3] > ids.to_user.map_by_name => ['Dr Nic', 'Banjo', 'Nancy'] 

Versus:

> User.find(ids).map_by_name