From: Chunyun Zhao <chunyun.zhao@...>
Date: 2006-12-22T06:55:48+09:00
Subject: Re: prob with each_with_index

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hit passed in the block is the elment, not the array.

Try this:

@flow_sensor.flow_hits.each_with_index do |hit, i|
         if i > 4 # start with 3rd hit in db
             time_diff = hit.date_time.to_i -
@flow_sensor.flow_hits[i-3].date_time.to_i
             value_diff = hit.value - @flow_sensor.flow_hits[i-3].value
             min = time_diff / 60
             val = value_diff / min
             plots.push(val)
             times.push(hit.date_time)
         end
       end


On 12/21/06, shawn bright <nephish@gmail.com> wrote:
>
> lo there all,
>
> i am having a problem making each_with_index do what i need it to do.
> the issue is...
>
> i need to evaluate the gpm of a flow sensor.
> we are skipping over three database entries to get the values.
> difference in value / difference in time = gpm. ok, easy enough.
>
> but this code
>
> @flow_sensor.flow_hits.each_with_index do |hit, i|
>           if i > 4 # start with 3rd hit in db
>               time_diff = hit[i].date_time.to_i - hit[i-3].date_time.to_i
>               value_diff = hit[i].value - hit[i-3].value
>               min = time_diff / 60
>               val = value_diff / min
>               plots.push(val)
>               times.push(hit[i].date_time)
>           end
>         end
>
> is giving me a nil value evaluating nil.date_time
>
> this is for a rails app by the way.
>
> i know i have the models set up right, because other functions are
> working.
> thats why i think my structure is wrong.
>
> thanks.
>
>

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