charts - Using instance methods with chartkick in a rails app -

i have model, teams has instance method point_differential (basically points - points against). trying use in chartkick graph, no luck.

this works

= bar_chart team.group(:group).sum(points_for)

because points_for attribute of team model.

this doesn't because point_differential instance method, not attribute

= bar_chart team.group(:name).sum(point_differential)

neither does

= bar_chart team.group(:name).sum(&:point_differential)

neither

bar_chart = team.all.map {|team| {name:team.name, point_differential: team.point_differential}}

any ideas?

your last option there correct, have wrong format.

consider first example:

team.group(:group).sum(:points_for)

this create hash following:

{"team a" => 14, "team b" => 9}

in last example did this:

team.all.map {|team| {name:team.name, point_differential: team.point_differential}}

which create an array of hashes following:

[{:name => "team a", :point_differential => 14}, {:name => "team b", :point_differential => 9}]

instead, try this:

hash[ *team.all.map { |team| [team.name, team.point_differential] }.flatten ]

this esoteric 1 liner takes array of arrays (each 2 elements), , creates hash out of them, giving this:

{"team a" => 14, "team b" => 9 }

like want.

another way, showing more steps this, this:

hash = {} team.all.each |team|   hash[team.name] = team.point_differential end

then hash have right values.

My