How to access block parameters using Object.send - ruby

Question

I'm trying to run the following code:
class RentLimit < ActiveRecord::Base
def self.load_data
rows = CSV.open("csvs/income_limits_2011_to_2015.csv").read
rows.shift
rows.each do |county, yr, date, _50pct_1br, _50pct_2br, _50pct_3br, _50pct_4br, _60pct_1br, _60pct_2br, _60pct_3br, _60pct_4br|
[50, 60].each do |ami|
[1, 2, 3, 4].each do |br|
r = new
r.county = county
r.state = "SC"
r.year = yr
r.effective_date = Date.parse(date)
r.pct_ami = ami
r.br = br
r.max_rent = self.send("_#{ami}pct_#{br}br".to_sym)
r.save
end#of brs
end# of amis
end# of rows
end
end
but am getting this error message when trying to run it:
NoMethodError: undefined method `_50pct_1br' for #<Class:0x007fe942ce3b18>
The send method isn't able to access those block parameters inside of the scope. Is there any way to give access to block parameters to send? If not, how else might I dynamically access block parameters?
How do I use send or its equivalent to access block parameters in Ruby?

Answer 1

This is much easier if you tell CSV.open what your column names are. It looks like your CSV file might have a header row that you're skipping with rows.shift, in which case you shouldn't skip it, and use the headers: true option. Then you can access each field by name with row["field_name"] or, in your case, row["_#{ami}pct_#{br}br"]:
CSV_PATH = "csvs/income_limits_2011_to_2015.csv"
DEFAULT_STATE = "SC"
def self.load_data
CSV.open(CSV_PATH, 'r', headers: true) do |csv|
csv.each do |row|
max_rent = row["_#{ami}pct_#{br}br"]
create(
county: row["county"],
state: DEFAULT_STATE,
year: row["yr"],
effective_date: Date.parse(row["date"]),
pct_ami: ami,
br: br,
max_rent: max_rent,
)
end
end
end
Note that I used CSV.open with a block to ensure that the file is closed after it's been read, which your original code wasn't doing. I also used create instead of new; ... save, since the latter is needlessly verbose.
If you're skipping the first row for some other reason, or you want to use field names other than those in the header row, you can set the options return_headers: false, headers: names, where names is an array of names, e.g.:
CSV_HEADERS = %w[
county yr date _50pct_1br _50pct_2br _50pct_3br _50pct_4br
_60pct_1br _60pct_2br _60pct_3br _60pct_4br
].freeze
def self.load_data
CSV.open(CSV_PATH, 'r', return_headers: false, headers: CSV_HEADERS) do |csv|
# ...
end
end
Finally, since some of your attributes are the same for every object created, I'd move those out of the loop:
def self.load_data
base_attrs = { state: DEFAULT_STATE, pct_ami: ami, br: br }
CSV.open(CSV_PATH, 'r', headers: true) do |csv|
csv.each do |row|
create(base_attrs.merge(
county: row["county"],
year: row["yr"],
effective_date: row["date"],
max_rent: row["_#{ami}pct_#{br}br"]
))
end
end
end