Given a table ZipCodeInfos with fields zipcode, state, city (all strings), where zipcode is unique:
zipcode,city,state
"10000", "Fooville", "AA"
"10001", "Smallville", "AA"
"10002", "Whoville", "BB"
What is the fastest way to generate a hash object of the entire table where the zipcode is a key like this:
{ "10000" => {:city => "Fooville", :state => "AA" },
"10001" => {:city => "Smallville", :state => "AA" },
"10002" => {:city => "Whoville", :state => "BB" } }
I know for a given record I can use .attributes to generate a hash with key,value pairs of field-names, field-values, for example Zipcode.first.attributes gives me
{"id" => 1, "zipcode" => "10000", "city" => "Fooville", "state => "AA" }
But, short of brute force iterating over each record (via .map), I cannot quite figure out how to create the desired hash with the zipcode as the key for each node of the hash.
This is the best I could come up with, and I suspect there is some nifty Ruby goodness that is faster?
zip_info_hash = {}
ZipCodeInfo.all.map{|x| zip_info_hash[x.zip] =
{'state' => x.state, 'city' => x.city }}
You could also try:
ZipCodeInfos.all.group_by &:zipcode
will get you a hash of zip code to array of ZipCodeInfos activerecords.
You can use inject method.
Here is what I generally use.
def visitors_name_email
visitors.inject({}) do |result, visitor|
result.merge(visitor.name => visitor.email)
end
end
I can't think of a way to avoid map here. I'd make only some minor changes to your code:
zip_info=Hash[*ZipCodeInfo.all
.map{|x| [x.zip, {:city => x.city, :state => x.state}]}
.flatten]
Related
Once again I am a new student to this whole computer coding thing and I am doing a boot camp to try to get the basics and my foot in the door but for some reason I can't make this whole iteration thing stick in my brain we just started doing hashes in ruby and I have literally been staring at the checkpoint problem for a day and a half and I just can't make my brain know what the next logical step is to get the answer provided. It is in a pre work section before my actual live classes start here in a few weeks and it's only my second full week doing any coding at all so the most bare bones basic hints/answers would be greatly appreciated.
This is the problem:
Write a loop to give each person an email address that consists of their first name + last name # gmail.com. For example, Robert Garcia will have an email of robertgarcia#gmail.com. The program should end with: p people
people = [
{
"first_name" => "Robert",
"last_name" => "Garcia",
"hobbies" => ["basketball", "chess", "phone tag"]
},
{
"first_name" => "Molly",
"last_name" => "Barker",
"hobbies" => ["programming", "reading", "jogging"]
},
{
"first_name" => "Kelly",
"last_name" => "Miller",
"hobbies" => ["cricket", "baking", "stamp collecting"]
}
]
outer_index = 0
names = []
last_names = []
while outer_index < people.length
names << people[outer_index]["first_name"].downcase
last_names << people[outer_index]["last_name"].downcase
outer_index += 1
end
email = email = [names[0] + last_names[0] + "#gmail.com"]
this is all the farther I have gotten because everything I've tried to get it to go back trough and pick up the second and third names hasn't worked.
According to them this is what it is supposed to look like in the end:
so that you can see if the correct modifications were made to each hash. The result should be:
people =[
{
"first_name" => "Robert",
"last_name" => "Garcia",
"hobbies" => ["basketball", "chess", "phone tag"],
"email" => "robertgarcia#gmail.com"
},
{
"first_name" => "Molly",
"last_name" => "Barker",
"hobbies" => ["programming", "reading", "jogging"],
"email" => "mollybarker#gmail.com"
},
{
"first_name" => "Kelly",
"last_name" => "Miller",
"hobbies" => ["cricket", "baking", "stamp collecting"],
"email" => "kellymiller#gmail.com"
}
]
(Note that your output won't be indented nicely).
I am completely at a loss and I cannot see where I am going wrong so any help would be insanely helpful so I can get through this checkpoint and finish up week two and move on to week three asap.
It's pretty straightforward to loop over each element of the people array. We also can use string interpolation to easily compose the email address.
people.each do |h|
h["email"] = "#{h["first_name"]}#{h["last_name"]}#gmail.com".downcase
end
If we want to break this up a bit, we can.
people.each do |h|
fn = h["first_name"]
ln = h["last_name"]
h["email"] = "#{fn}#{ln}#gmail.com"
h["email"].downcase!
end
You're really overcomplicating it, there is no need to use while to simply loop across an array. Instead use #each from the Enumerable module:
people.each do |hash|
hash.merge!(
"email" => "#{hash['first_name']}#{hash['last_name']}#gmail.com".downcase
)
end
Or if you want a non-destructive version that doesn't alter the original data:
people.map do |hash|
hash.merge(
"email" => "#{hash['first_name']}#{hash['last_name']}#gmail.com".downcase
)
end
I am trying to do a query against a ruby hash, which is much alike this:
{"client1" => {"tag" => "13", "host" => "client1.example.com", ...}, "client2" => {"tag" => "11", ...} }
and I would like to map it to only the client names with their tags, like this:
{"client1" => "13", "client2" => "11"}
I have been struggeling with .each and .select and .find but haven't figured it out yet. I am pretty sure it is not that hard, does anybody know? Thanks
You could do the same as below
data = {
"client1" => {"tag" => "13", "host" => "client1.example.com"},
"client2" => {"tag" => "11"}
}
desired_data = Hash.new
data.each do |k,v|
desired_data[k] = v["tag"]
end
desired_data will contain your result.
As suggested by #sawa you could also use
data.each_with_object({}){|(k, v), h| h[k] = v["tag"]}
Use map:
test_hash = {"client1" => {"tag" => "13", "host" => "client1.example.com"}, "client2" => {"tag" => "11"} }
test_hash.map{|k,v| [k, v['tag']]}.to_h
#=> {"client1"=>"13", "client2"=>"11"}
One way is to merge the hash with itself, using the form of Hash#merge that employs a block to determine the values of keys that are present in both hashes being merged, which in this case is all keys.
h = {"client1" => {"tag" => "13", "host" => "client1.example.com"},
"client2" => {"tag" => "11"} }
h.merge(h) { |*,v| v["tag"] }
#=> {"client1"=>"13", "client2"=>"11"}
As explained in the doc, the block has three variables, often written |key, old_value, new_value|. Here old_value and new_value are the same. The asterisk in |*, new_value| is a placeholder for all but the last block variable.
I want to compare two XML files where one is input and the other is output. I am converting both into a hash.
My idea is to get all the keys from the input XML converted to hash, and search each key in both the input and output hashes for their respective key/value pairs.
I have a hash:
{
"requisition_header" => {
"requested_by" => {"login" => "coupasupport"},
"department" => {"name" => "Marketing"},
"ship_to_address" => {"name" => "Address_1431693296"},
"justification" => nil,
"attachments" => [],
"requisition_lines" => [
{
"description" => "Cleaning Services for Building A",
"line_num" => 1,
"need_by_date" => 2010-09-23 07:00:00 UTC,
"source_part_num" => nil,
"supp_aux_part_num" => nil,
"unit_price" => #<BigDecimal:a60520c,'0.3E4',9(18)>,
"supplier" => {"name" => "amazon.com"},
"account" => {
"code" => "SF-Marketing-Indirect",
"account_type" => {"name" => "Ace Corporate"}
},
"currency" => {"code" => "USD"},
"payment_term" => {"code" => "Net 30"},
"shipping_term" => {"code" => "Standard"},
"commodity" => {"name" => "Marketing-Services"}
}
]
}
}
It is nested and all the values are not directly accessible.
I want a way to generate direct access to each value in the hash.
For example:
requisition_header.requested_by.login
will access "coupasupport".
requisition_header.department.name
will access "Marketing".
requisition_header.requisition_lines[0].description
will access "Cleaning Services for Building A".
requisition_header.requisition_lines[0].line_num
will access "1".
requisition_header.requisition_lines[0].need_by_date
will access "2010-09-23 07:00:00 UTC".
Each key built can be used to search for the value directly inside the hash.
That could be done with the following method, that translates the nested hash into nested OpenStructs:
require 'ostruct'
def deep_structify(hash)
result = {}
hash.each do |key, value|
result[key] = value.is_a?(Hash) ? deep_structify(value) : value
end if hash
OpenStruct.new(result)
end
hash = {"requisition_header"=>{"requested_by"=>{"login"=>"coupasupport"}, "department"=>{"name"=>"Marketing"}, "ship_to_address"=>{"name"=>"Address_1431693296"}, "justification"=>nil, "attachments"=>[], "requisition_lines"=>[{"description"=>"Cleaning Services for Building A", "line_num"=>1, "need_by_date"=>2010-09-23 07:00:00 UTC, "source_part_num"=>nil, "supp_aux_part_num"=>nil, "unit_price"=>#<BigDecimal:a60520c,'0.3E4',9(18)>, "supplier"=>{"name"=>"amazon.com"}, "account"=>{"code"=>"SF-Marketing-Indirect", "account_type"=>{"name"=>"Ace Corporate"}}, "currency"=>{"code"=>"USD"}, "payment_term"=>{"code"=>"Net 30"}, "shipping_term"=>{"code"=>"Standard"}, "commodity"=>{"name"=>"Marketing-Services"}}]}}
struct = deep_structify(hash)
struct.requisition_header.department.name
#=> "Marketing"
You can do it by overriding OpenStruct#new as well,
require 'ostruct'
class DeepStruct < OpenStruct
def initialize(hash=nil)
#table = {}
#hash_table = {}
if hash
hash.each do |k,v|
#table[k.to_sym] = (v.is_a?(Hash) ? self.class.new(v) : v)
#hash_table[k.to_sym] = v
new_ostruct_member(k)
end
end
end
def to_h
#hash_table
end
end
Now you can do:
require 'deep_struct'
hash = {"requisition_header"=>{"requested_by"=>{"login"=>"coupasupport"}, "department"=>{"name"=>"Marketing"}, "ship_to_address"=>{"name"=>"Address_1431693296"}, "justification"=>nil, "attachments"=>[], "requisition_lines"=>[{"description"=>"Cleaning Services for Building A", "line_num"=>1, "need_by_date"=>2010-09-23 07:00:00 UTC, "source_part_num"=>nil, "supp_aux_part_num"=>nil, "unit_price"=>#<BigDecimal:a60520c,'0.3E4',9(18)>, "supplier"=>{"name"=>"amazon.com"}, "account"=>{"code"=>"SF-Marketing-Indirect", "account_type"=>{"name"=>"Ace Corporate"}}, "currency"=>{"code"=>"USD"}, "payment_term"=>{"code"=>"Net 30"}, "shipping_term"=>{"code"=>"Standard"}, "commodity"=>{"name"=>"Marketing-Services"}}]}}
mystruct = DeepStruct.new hash
mystruct.requisition_header.requested_by.login # => coupasupport
mystruct.requisition_header.to_h # => {"requested_by"=>{"login"=>"coupasupport"}
You could use BasicObject#method_missing:
Code
class Hash
def method_missing(key,*args)
(args.empty? && key?(key)) ? self[key] : super
end
end
Example
hash = { animals: {
pets: { dog: "Diva", cat: "Boots", python: "Stretch" },
farm: { pig: "Porky", chicken: "Little", sheep: "Baa" }
},
finishes: {
tinted: { stain: "Millers", paint: "Oxford" },
clear: { lacquer: "Target", varnish: "Topcoat" }
}
}
hash.finishes.tinted.stain
#=> "Millers
hash.animals.pets.cat
#=> "Boots"
hash.animals.pets
#=> {:dog=>"Diva", :cat=>"Boots", :python=>"Stretch"}
hash.animals
#=> {:pets=>{:dog=>"Diva", :cat=>"Boots", :python=>"Stretch"},
# :farm=>{:pig=>"Porky", :chicken=>"Little", :sheep=>"Baa"}}
Reader challenge
There is a potential "gotcha" with this approach. I leave it to the reader to identify it. My example contains a clue. (Mind you, there may be other problems I haven't thought of.)
The objective of the code below is to produce a hash with the keys being the :id field of
the hashes in original_array, and the values being all elements in original_array which have that :id.
original_array = [
{:id => '123', :name => 'test'},
{:id => '123', :name => 'another test'},
{:id => '456', :name => 'yet another test'}
]
new_hash = {}
original_array.each do |a|
new_hash[a[:id]] = original_array.select {|x| x[:id] == a[:id]}
end
My code does that, but there must be some better way to do it, ideally where the hash can be created in one step. If anyone can suggest and explain one (in the hope that I might improve my understanding of this sort of thing), then it would be appreciated.
This should do it
new_hash = original_array.group_by{|h| h[:id]}
Documentation: Enumerable#group_by.
I'm writing an API parser at the moment, and I'm working on formatting the data nicely.
So far, I have the following code:
data.each {|season| episodes[season["no"].to_i] = season["episode"].group_by{|i| i["seasonnum"].to_i}}
However, the only issue with this is that the output comes out like this:
8 => {
1 => [
[0] {
"epnum" => "150",
"seasonnum" => "01",
"prodnum" => "3X7802",
"airdate" => "2012-10-03",
"link" => "http://www.tvrage.com/Supernatural/episodes/1065195189",
"title" => "We Need to Talk About Kevin"
}
],
2 => [
[0] {
"epnum" => "151",
"seasonnum" => "02",
"prodnum" => "3X7803",
"airdate" => "2012-10-10",
"link" => "http://www.tvrage.com/Supernatural/episodes/1065217045",
"title" => "What's Up, Tiger Mommy?"
}
]
}
So there's a redundant array in each value of the secondary hash. How would I remove this array and just have the inside hash? So, for example I want:
8 => {
1 => {
"epnum" => "150",
"seasonnum" => "01",
"prodnum" => "3X7802",
"airdate" => "2012-10-03",
"link" => "http://www.tvrage.com/Supernatural/episodes/1065195189",
"title" => "We Need to Talk About Kevin"
}
,
etc.
EDIT: Here's the full file:
require 'httparty'
require 'awesome_print'
require 'debugger'
require 'active_support'
episodes = Hash.new{ [] }
response = HTTParty.get('http://services.tvrage.com/feeds/episode_list.php?sid=5410')
data = response.parsed_response['Show']['Episodelist']["Season"]
data.each { |season|
episodes[season["no"].to_i] = season["episode"].group_by{ |i|
i["seasonnum"].to_i
}
}
ap episodes
Input data: http://services.tvrage.com/feeds/episode_list.php?sid=5410
Wild guess:
data.each { |season|
episodes[season["no"].to_i] = season["episode"].group_by{ |i|
i["seasonnum"].to_i
}.first
}
It looks like you're using group_by (array of entries with same key) when you really want index_by (one entry per key).
data.each {|season| episodes[season["no"].to_i] = season["episode"].index_by {|i| i["seasonnum"].to_i}}
NOTE: If you can have MORE than one episode with the same seasonnum, you SHOULD use group by and have an array of values here. If you're just building a hash of episodes with a convenient lookup (one to one mapping), then index_by is what you want.