MVC, best practice for hash that combines objects?

rubyonrails-talk
1

Hi,

I just wanted to see if I am on the right track, as I am new to MVC.

I have a model called Tasks, and another called Entries. Tasks has many entries.

Each entry has a time. So I want to total up the time entries so that I have a keyed array of task Ids => duration.

In the end, I want to then print it out as a table in the reports view, doing things like filter by completed, by date, etc.

Where should this hash be constructed? A function in a Report model?

Thanks! arcX

2

Assuming you are developing in Rails then the convention would be for the models to be Task and Entry, with the controllers tasks_controller and entries_controller.

If I have understood the problem correctly I think the first thing I would do is provide a method in model Task called duration that returns the total duration for that task by summing task.entries.time. Then all you need to pass to the report view is @tasks containing the tasks you are interested in and for each one task.duration is available to be displayed as desired.

Colin

3

Colin Law wrote:

If I have understood the problem correctly I think the first thing I would do is provide a method in model Task called duration that returns the total duration for that task by summing task.entries.time. Then all you need to pass to the report view is @tasks containing the tasks you are interested in and for each one task.duration is available to be displayed as desired.

Rails also provides aggregate functions so rather than writing a duration method you could also write: task = Task.find(:first) task.entries.sum(:time)

Line 2 generates the following SQL: SELECT sum("entries".time) AS sum_time FROM "entries" WHERE ("entries".task_id = 1)

4

Colin Law wrote:

If I have understood the problem correctly I think the first thing I

would

do is provide a method in model Task called duration that returns the

total

duration for that task by summing task.entries.time. Then all you need

to

pass to the report view is @tasks containing the tasks you are

interested in

and for each one task.duration is available to be displayed as desired.

Rails also provides aggregate functions so rather than writing a

duration method you could also write:

task = Task.find(:first)

task.entries.sum(:time)

I would still suggest having a duration method, where the method just returns entries.sum(:time), as it removes the requirement that the caller needs to know that how to work out the duration.

5

Wow!

Thanks so much to both of you, that works great for me!

It also helped me to understand just how powerful the model can be.

arcX