Unable to fetch deeply nested hash value - ruby

Question

I have this rake task which uses rest-client to fetch some messy JSON from this API, and then uses hashie to make the code prettier.
Unfortunately I'm unable to fetch one of the deeply nested values, productGroup. If working correctly, it should output :category => "Jeans" or similar. Please see the JSON at the bottom.
This did not work:
mash.deep_fetch(:fields, 0).deep_locate(-> (key, value, object) { value.include?("product_group") }) { "ERROR: category" }
Example output:
% rake get_products
{:category=>nil, :name=>"Luxurous Jumpsuit", :image=>"http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/129579-0012.jpg", :price=>"599", :description=>"Lorem ipsum dolor"}
Example mash:
#<Hashie::Mash brand="Dr Denim" categories=[#<Hashie::Mash name="Kvinne > KLÆR > Jeans > Slim">] description="Lorem ipsum dolor." fields=[#<Hashie::Mash name="sale" value="false">, #<Hashie::Mash name="product_id_original" value="226693-7698">, #<Hashie::Mash name="gender" value="Kvinne">, #<Hashie::Mash name="artNumber" value="226693-7698">, #<Hashie::Mash name="productGroup" value="Jeans">, #<Hashie::Mash name="productStyle" value="Slim">, #<Hashie::Mash name="extraImageProductSmall" value="http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/cart_thumb/226693-7698.jpg">, #<Hashie::Mash name="productClass" value="Klær">, #<Hashie::Mash name="extraImageProductLarge" value="http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/226693-7698.jpg">, #<Hashie::Mash name="sizes" value="W24/L32,W25/L32,W26/L32,W27/L32,W28/L32,W29/L32,W30/L32,W31/L32,W32/L32,W26/L30,W27/L30,W28/L30,W29/L30,W24/L30,W25/L30,W32/L30,W31/L30,W30/L30">, #<Hashie::Mash name="color" value="Mid Blue">] identifiers=#<Hashie::Mash sku="226693-7698"> language="no" name="Regina Jeans" offers=[#<Hashie::Mash feed_id=10086 id="2820760a-c5b2-494a-b5dd-ab713f796cb9" in_stock=1 modified=1474947357838 price_history=[#<Hashie::Mash date=1474949513421 price=#<Hashie::Mash currency="NOK" value="599">>] product_url="http://pdt.tradedoubler.com/click?a1234" program_logo="http://hst.tradedoubler.com/file/17833/2014-logos/200X200.png" program_name="Nelly NO" source_product_id="226693-7698">] product_image=#<Hashie::Mash url="http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/226693-7698.jpg">>
get_products.rake:
# encoding: utf-8
# Gets messy JSON from other store via REST client and cleans it up with Hashie
require "rest_client"
require "hashie"
Product = Struct.new(:category, :name, :image, :price, :description)
module ProductsFromOtherStore
CATEGORIES = [
"festkjoler",
"jakker",
"jeans",
"jumpsuit",
"vesker"
]
def self.fetch
CATEGORIES.map do |category|
Tradedoubler.fetch category
end
end
# Prettify, ie. `fooBar` => `foo_bar`
def self.prettify(x)
case x
when Hash
x.map { |key, value| [key.underscore, prettify(value)] }.to_h
when Array
x.map { |value| prettify(value) }
else
x
end
end
end
class ProductsFromOtherStore::Tradedoubler
KEY = "FE34B1309AB749F1578AEE87D9D74535513F6B54"
# Products to fetch from API
LIMIT = 2
def self.fetch category
new(category).filtered_products.take(LIMIT)
rescue RestClient::RequestTimeout => e
Array.new
end
def initialize category
#category = category
# API doesn't support gender or category searches, so do some filtering based on available JSON fields
#filters = Array.new
define_filter { |mash|
mash.fields.any? { |field|
field.name == "gender" && field.value.downcase == "kvinne"
}
}
define_filter { |mash|
mash.categories.any? { |category|
category.name.underscore.include? #category
}
}
end
def define_filter(&filter)
#filters << filter
end
def filtered_products
filtered_mashes.map { |mash|
# puts mash
Product.new(
# mash.deep_fetch(:fields, 0).find { |field| field[:name] == "product_group" }[:value],
mash.deep_fetch(:fields, 0).deep_locate(-> (key, value, object) { value.include?("product_group") }) { "ERROR: category" },
mash.deep_fetch(:name) { "ERROR: name" },
mash.deep_fetch(:product_image, :url) { "ERROR: image URL" },
mash.deep_fetch(:offers, 0, :price_history, 0, :price, :value) { "ERROR: price" },
mash.deep_fetch(:description) { "ERROR: description" }
)
}
end
private
def request
response = RestClient::Request.execute(
:method => :get,
:url => "http://api.tradedoubler.com/1.0/products.json;q=#{ URI.encode(#category) };limit=#{ LIMIT }?token=#{ KEY }",
:timeout => 0.4
)
end
def hashes
ProductsFromOtherStore.prettify(JSON.parse(request)["products"])
end
def mashes
hashes.map { |hash| Hashie::Mash.new(hash) }.each do |mash|
mash.extend Hashie::Extensions::DeepFetch
mash.extend Hashie::Extensions::DeepLocate
end
end
def filtered_mashes
mashes.select { |mash| mash_matches_filter? mash }
end
def mash_matches_filter? mash
# `.all?` requires all filters to match, `.any?` requires only one
#filters.all? { |filter| filter.call mash }
end
end
# All that for this
task :get_products => :environment do
#all_products_from_all_categories = ProductsFromOtherStore.fetch
#all_products_from_all_categories.each do |products|
products.each do |product|
puts product.to_h
end
end
end
The messy JSON we got via rest-client:
{
"productHeader": {
"totalHits": 367
},
"products": [{
"name": "501 CT Jeans For Women",
"productImage": {
"url": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/441576-1056.jpg"
},
"language": "no",
"description": "Jeans fra Levi's. Noe kortere nederst, fem lommer. Normal høyde på midjen, med hemper i linningen og knappegylfen. Dekorative slitte partier foran og nederst på benet.<br />Laget av 100% bomull.",
"brand": "Levis",
"identifiers": {
"sku": "441576-1056"
},
"fields": [{
"name": "sale",
"value": "false"
}, {
"name": "sizes",
"value": "W24/L32,W25/L32,W26/L32,W27/L32,W28/L32,W29/L32,W30/L32,W31/L32,W25/L34,W26/L34,W27/L34,W28/L34,W29/L34,W30/L34"
}, {
"name": "productStyle",
"value": "Straight"
}, {
"name": "gender",
"value": "Kvinne"
}, {
"name": "product_id_original",
"value": "441576-1056"
}, {
"name": "productGroup",
"value": "Jeans"
}, {
"name": "extraImageProductLarge",
"value": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/441576-1056.jpg"
}, {
"name": "extraImageProductSmall",
"value": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/cart_thumb/441576-1056.jpg"
}, {
"name": "artNumber",
"value": "441576-1056"
}, {
"name": "productClass",
"value": "Klær"
}, {
"name": "color",
"value": "Indigo"
}],
"offers": [{
"feedId": 10086,
"productUrl": "http://pdt.tradedoubler.com/click?a(2402331)p(80279)product(57d37b9ce4b085c06c38c96b)ttid(3)url(http%3A%2F%2Fnelly.com%2Fno%2Fkl%C3%A6r-til-kvinner%2Fkl%C3%A6r%2Fjeans%2Flevis-441%2F501-ct-jeans-for-women-441576-1056%2F)",
"priceHistory": [{
"price": {
"value": "1195",
"currency": "NOK"
},
"date": 1473477532181
}],
"modified": 1473477532181,
"inStock": 1,
"sourceProductId": "441576-1056",
"programLogo": "http://hst.tradedoubler.com/file/17833/2014-logos/200X200.png",
"programName": "Nelly NO",
"id": "57d37b9ce4b085c06c38c96b"
}],
"categories": [{
"name": "Kvinne > KLÆR > Jeans > Straight"
}]
}, {
"name": "501 CT Jeans For Women",
"productImage": {
"url": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/441576-6581.jpg"
},
"language": "no",
"description": "Jeans fra Levi's. Noe kortere nederst, fem lommer. Normal høyde på midjen, med hemper i linningen og knappegylfen. Dekorative slitte partier foran og nederst på benet.<br />Laget av 100% bomull.",
"brand": "Levis",
"identifiers": {
"sku": "441576-6581"
},
"fields": [{
"name": "sale",
"value": "false"
}, {
"name": "artNumber",
"value": "441576-6581"
}, {
"name": "productStyle",
"value": "Straight"
}, {
"name": "gender",
"value": "Kvinne"
}, {
"name": "extraImageProductLarge",
"value": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/productLarge/441576-6581.jpg"
}, {
"name": "extraImageProductSmall",
"value": "http://nlyscandinavia.scene7.com/is/image/nlyscandinavia/cart_thumb/441576-6581.jpg"
}, {
"name": "productGroup",
"value": "Jeans"
}, {
"name": "product_id_original",
"value": "441576-6581"
}, {
"name": "productClass",
"value": "Klær"
}, {
"name": "color",
"value": "Desert"
}, {
"name": "sizes",
"value": "W24/L32,W25/L32,W26/L32,W27/L32,W28/L32,W29/L32,W30/L32,W31/L32,W25/L34,W26/L34,W27/L34,W28/L34,W29/L34,W30/L34,W31/L34"
}],
"offers": [{
"feedId": 10086,
"productUrl": "http://pdt.tradedoubler.com/click?a(2402331)p(80279)product(57b3cafbe4b06cf59bc254bf)ttid(3)url(http%3A%2F%2Fnelly.com%2Fno%2Fkl%C3%A6r-til-kvinner%2Fkl%C3%A6r%2Fjeans%2Flevis-441%2F501-ct-jeans-for-women-441576-6581%2F)",
"priceHistory": [{
"price": {
"value": "1195",
"currency": "NOK"
},
"date": 1471400699283
}],
"modified": 1471400699283,
"inStock": 1,
"sourceProductId": "441576-6581",
"programLogo": "http://hst.tradedoubler.com/file/17833/2014-logos/200X200.png",
"programName": "Nelly NO",
"id": "57b3cafbe4b06cf59bc254bf"
}],
"categories": [{
"name": "Kvinne > KLÆR > Jeans > Straight"
}]
}]
}

Answer 1

There is a lot of things going on in your code sample. I tried to split in parts and restructure it. It does not do the same as your code but I think it should get you started and perhaps you can come back when you have a more specific question.
Note that I did not use hashie, I think that accessing some deeply nested hash structures in a few places does not justify adding a new library to a project.
Questions/Ideas/Hints:
are prices Integers or Floats?
Is the JSON consistent (all elements present all the time?)
Are you using Ruby 2.3? Then look into Hash#dig
Why did you prettify the JSON keys? Does not make sense to me as you build Product objects to work with anyway?
Unless there are performance issues i would convert all products to Ruby objects first and filter then. Just easier and more readable.
Code
Product (same as yours)
Product = Struct.new(:category, :name, :image, :price, :description)
JsonProductBuilder converts the parsed JSON to Product Objects.
class JsonProductBuilder
def initialize(json)
#json = json
end
def call
json.fetch('products', []).map do |item|
Product.new(
extract_category(item),
item['name'],
item.fetch('productImage', {})['url'],
extract_price(item),
item['description']
)
end
end
private
attr_reader :json
def extract_category(item)
field = item['fields'].find do |field|
field['name'] == 'productGroup'
end
field['value'] if field
end
def extract_price(item)
offer = item['offers'].first
history = offer['priceHistory'].first
value = history['price']['value']
Integer(value) # Or use Float?
end
end
CategoryFilter returns a limited subset of the products. You can easily add other filters and combine them. Perhaps you might want to look into lazy for performance improvements.
class CategoryFilter
def initialize(products, *categories)
#products = products
#categories = categories
end
def call
products.select do |product|
categories.include?(product.category)
end
end
private
attr_reader :products, :categories
end
Use it like this:
limit = 10
categories = ['laptop', 'something']
params = {
q: categories.join(','),
limit: limit,
}
paramsString = params.map do |key, value|
"#{key}=#{value}"
end.join(';')
response = RestClient.get(
"http://api.tradedoubler.com/1.0/products.json;#{paramsString}?token=#{token}"
)
json = JSON.parse(response)
products = JsonProductBuilder.new(json).call
puts products.size
products = CategoryFilter.new(products, 'Klær', 'Sko', 'Jeans').call
puts products.size
products.each do |product|
puts product.to_h
end