Creating an array by reusing code


#1

Hi
I have
all_req = OnRequest.find(:all, :conditions => [status_id = ?’,6])

Now i need to create an array of size 12 containing record counts for
month January to December like [recordcountjanuary,recordcountfeb,…]
So for the first month january I tried like

all_req.select do |r|
r.created_at.mon == 1
end
What i need is reuse the above code I have placed it in a
function But there I have to call it 12 times .How can i avoid this?

Thanks in advance
Sijo


#2

On Wed, Mar 25, 2009 at 11:42 AM, Sijo Kg removed_email_address@domain.invalid wrote:

end
What i need is reuse the above code I have placed it in a
function But there I have to call it 12 times .How can i avoid this?

Maybe this helps (untested):

recordcount = (1…12).map do |month|
all_req.select {|r| r.created_at.mon == month}.size
end

Although this does 12 passes through all_req. BTW, if you need the
count you need to check the size of the select. Maybe another approach
could be using a hash:

recordcount = Hash.new(0)
all_req.each do |r|
recordcount[r.created_at.mon] += 1
end

Hope this helps,

Jesus.


#3

On Wed, Mar 25, 2009 at 4:12 PM, Sijo Kg removed_email_address@domain.invalid wrote:

[…]
Now i need to create an array of size 12 containing record counts for
month January to December like [recordcountjanuary,recordcountfeb,…]
So for the first month january I tried like

all_req.select do |r|
r.created_at.mon == 1
end
What i need is reuse the above code I have placed it in a
function But there I have to call it 12 times .How can i avoid this?

Let’s build this up a step at a time…

monthly_counts = (1…12).map do |month|

call your function here, passing in the month

end

Depending on the scope of all_req, it may just be easier to inline the
function as follows:

monthly_counts = (1…12).map do |month|
all_req.select {|r| r.created_at.mon == month }.size
end

However, this is inefficient. We have to make 12 passes over the
all_req collection.
You can, instead use Enumerable#group_by:

all_req.group_by {|r| r.created_at.mon }

which will return a hash of items keyed by the month. Getting counts
from this is simply a matter of using #map. I’ll leave this as an
exercise :slight_smile:

Now, having said all that, the most efficient way to do this is
probably to use a group_by clause in your finder. Again, left as an
exercise (mostly 'cos i don’t know AR :slight_smile:

solidarity,
lasitha


#4

2009/3/25 lasitha removed_email_address@domain.invalid:

However, this is inefficient. We have to make 12 passes over the
all_req collection.
You can, instead use Enumerable#group_by:

all_req.group_by {|r| r.created_at.mon }

which will return a hash of items keyed by the month. Getting counts
from this is simply a matter of using #map. I’ll leave this as an
exercise :slight_smile:

Or create a counter Hash and loop once:

counts = Hash.new 0
all_req.each {|r| counts[r.created_at.mon] += 1}

Now, having said all that, the most efficient way to do this is
probably to use a group_by clause in your finder. Again, left as an
exercise (mostly 'cos i don’t know AR :slight_smile:

Yep, the database solution is probably the best.

Cheers

robert