setting a nested value in PStore - ruby

Question

PStore is a data-serializer in the Stdlib which is human-readable like JSON or YAML.
Everything has to be done in a "transaction", e.g.
storage = PStore.new("db")
storage.transaction do |db|
db[:key] = {}
db[:key][:sub_key] = "val"
return db[:key][:sub_key]
end
# ==> "val"
I want to be able to make a method like this:
def store(storage, list_of_keys, value)
storage.transaction do |db|
db[list_of_keys[0][list_of_keys[1]][list_of_keys[n]] = value
end
end
Conceptually I think currying would be useful here, but I've only done it in Javascript.
It doesn't seem to work to store the references to the intermediate values in variables like this:
storage.transaction do |db|
db_val_1 = db[keys[0]]
db_val_1 = value
end

Answer 1

I don't know exactly what you want. But my guess is you wanna store a value inside a nested hash with given list of keys. Since it's a nested has, I would use, well, a hash obviously. Here is a full working code for what I think you are trying to do:
require 'pstore'
require 'minitest/autorun'
storage = PStore.new("data_file.pstore")
def nest(key_list, value)
reverse_key_list = key_list.reverse
inner_most = {"#{reverse_key_list.shift}" => value}
reverse_key_list.reduce(inner_most) {|acc, current| {"#{current}" => acc }}
end
def nested_store(storage, key_list, value)
root = key_list.shift
data = nest(key_list, value)
storage.transaction { storage[root] = data }
end
describe "pstore test" do
before do
#key_list = %w(root sub1 sub2 sub3)
#val = "value"
end
it "should nest the list" do
nest(#key_list, #val).must_equal({"root" => {"sub1" => {"sub2" => {"sub3" => "value" }}}})
end
it "store the nested list" do
storage = PStore.new("data_file.pstore")
nested_store(storage, #key_list, #val)
storage.transaction do
storage["root"]["sub1"]["sub2"]["sub3"].must_equal "value"
end
end
end