From: John Butler <johnnybutler7@...>
Date: 2008-05-29T21:49:20+09:00
Subject: Re: Merge collections of objects

Ron Fox wrote:
> Unless this is a toy project, it will be important to think about what
> is it that makes two employees, one in companyA and one in companyB
> 'duplicates'...and what you really want to do in that case as the
> record information related to the emplyees may be different between
> the companies...all this is interesting business logic.. not a ruby
> question however.
> 
> RF

Yes ive figured that out.  Its proving a bit of pain especially with has 
many through relationships.

For the above i have a company that has many employees through 
company_employees so what i basically want to do is.

companyA has 2 employees "a", "b"

companyB has 3 employees "a", "b", "c"

Copy any employees from companyB that are not in companyA
Delete all reference to employees from companyB

So

companyA will have 3 employees "a", "b", "c"

companyB will have no employees

Ive tried various tings as there are a lot of associations i need to 
copy over so im trying to create one method that will deal with this 
passing through the 2 objects and the relationship in dyn_method:

dyn_method = 'employees'
myarray = Array.new
myarray = companyA.send(dyn_method) | company_b.send(dyn_method)
companyA.send(dyn_method + '=',myarray)

The below works as in it updates all the company_id links in the 
company_employees table with companyA's id so the employees are only 
linked to companyA and not referenced by companyB anymore.  The 
duplicates causes an issue here though.
dyn_method = 'company_employees'
companyA.send(dyn_method + '=',companyB.send(dyn_method))

Im still looking for the best solution for adding to a company which has 
no employees and then to a company that already has employees but 
ignoring the duplicates.

JB





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