Reflect table changes in models

rubyonrails-talk
1

Hello,

I am adapting an existing system and I want to change some tables. I want to turn a column into a reference to a new table. What's the best way to do this? I guess migrations but how do I make the new models then? I am pretty new to rails so if you could provide me with the generator commands to that would be great. Of course online references are fine too!

Regards, Bart

2

Hi Bart,

Bart Braem wrote:

how do I make the new models then?

It seems unlikely, for someone undertaking a change to an app's data model, that what you're looking for is this basic, but just in case... To generate a new model for a table:

ruby script\generate model ModelName

Also, don't forget the Rails convention is that the ModelName is the singular of the table's name.

hth, Bill

3

I am adapting an existing system and I want to change some tables. I want to turn a column into a reference to a new table. What's the best way to do this?

If you have existing models, they will pick up any changes to the database.

For example, if you a 'products' table with an associated 'Product' model:

# assign price product.price = 5

Then you decide to change 'price' to 'sale_price' and generate/run a migration to do so. You can then just use the new column without changing your model:

# assign price product.sale_price = 5

Hope that helps and sorry if it's not quite what you meant :0)

Steve

4

Stephen Bartholomew wrote:

I am adapting an existing system and I want to change some tables. I want to turn a column into a reference to a new table. What's the best way to do this?

If you have existing models, they will pick up any changes to the database.

For example, if you a 'products' table with an associated 'Product' model:

# assign price product.price = 5

Then you decide to change 'price' to 'sale_price' and generate/run a migration to do so. You can then just use the new column without changing your model:

# assign price product.sale_price = 5

Hope that helps and sorry if it's not quite what you meant :0)

It's not really what I meant. I'll give an example with the product table. I currently have price, but say that I want to be a row in another table pricetag. That row would have columns like tagcolor, currency and value. (As an example, I don't need currency conversion!) So how do I make that conversion to a reference to an external table? If I generate the table with migrations it seems to fail...

Regards, Bart