Nesting loop within a block in Ruby - ruby

Question

I have a helper module to generate an array hash data, which is something like:
[{:date => d, :total_amount => 31, :first_category => 1, :second_category => 2,...},
{:date => d+1, :total_amount => 31, :first_category => 1, :second_category => 2,...}]
So I make the method like:
def records_chart_data(category = nil, start = 3.weeks.ago)
total_by_day = Record.total_grouped_by_day(start)
category_sum_by_day = Record.sum_of_category_by_day(start)
(start.to_date..Time.zone.today).map do |date|
{
:date => date,
:total_amount => total_by_day[date].try(:first).try(:total_amount) || 0,
Category.find(1).title => category_sum_by_day[0][date].try(:first).try(:total_amount) || 0,
Category.find(2).title => category_sum_by_day[1][date].try(:first).try(:total_amount) || 0,
Category.find(3).title => category_sum_by_day[2][date].try(:first).try(:total_amount) || 0,
}
end
end
Since the Category will always change, I try to use loop in this method like:
def records_chart_data(category = nil, start = 3.weeks.ago)
total_by_day = Record.total_grouped_by_day(start)
category_sum_by_day = Record.sum_of_category_by_day(start)
(start.to_date..Time.zone.today).map do |date|
{
:date => date,
Category.all.each_with_index do |category, index|
category.title => category_sum_by_day[index][date].try(:first).try(:total_amount) || 0,
end
:total_amount => total_by_day[date].try(:first).try(:total_amount) || 0
}
end
end
But ruby alerts me with an error:
/Users/tsu/Code/CashNotes/app/helpers/records_helper.rb:10: syntax error, unexpected tASSOC, expecting keyword_end
category.title => category_sum_by_day[index][d...
Why does it say expecting keyword_end, and how should I fix it?
The method category_sum_by_day it calls looks like:
def self.sum_of_category_by_day(start)
records = where(date: start.beginning_of_day..Time.zone.today)
records = records.group('category_id, date(date)')
records = records.select('category_id, date, sum(amount) as total_amount')
records = records.group_by{ |r| r.category_id }
records.map do |category_id, value|
value.group_by {|r| r.date.to_date}
end
end
Or should I alter this method to generate a more friendly method for the helper above?

Answer 1

Category.all.each_with_index do |category, index|
category.title => category_sum_by_day # ...snip!
end
Unfortunately, this piece of code does not adhere to Ruby's grammar. The problem is the body of the block. x => y is not an expression and the syntax requires bodies of blocks to be expressions.
If you want to generate a hash by one key-value pair at a time try the following combination of Hash::[], Array#flatten and the splat operator (i.e. unary *):
Hash[*5.times.map { |i| [i * 3, - i * i] }.flatten]
As a result I'd rewrite the last expresion of records_chart_data more or less as follows
(start.to_date..Time.zone.today).map do |date|
categories = Hash[*Category.all.each_with_index do |category, index|
[ category.title, category_sum_by_day[...] ]
end .flatten]
{ :date => date,
:total_amount => total_by_day[date].try(:first).try(:total_amount) || 0
}.merge categories
end
If you consider it unreadable you can do it in a less sophisticated way, i.e.:
(start.to_date..Time.zone.today).map do |date|
hash = {
:date => date,
:total_amount => total_by_day[date].try(:first).try(:total_amount) || 0
}
Category.all.each_with_index do |category, index|
hash[category.title] = category_sum_by_day[...]
end
hash
end
Another idea is to use Array#reduce and adopt a more functional approach.
(start.to_date..Time.zone.today).map do |date|
Category.all.each_with_index.reduce({
:date => date,
:total_amount => total_by_day[date].try(:first).try(:total_amount) || 0
}) do |hash, (category, index)|
hash.merge category.title => category_sum_by_day[...]
end
hash
end