Initializing multiple objects at once? - ruby

Question

So, I'm trying to initialize multiple objects and add them to a list. What I'm wanting to happen is by running Market.new, I want every item from the api added as an object. Below is the code I thought might work. But, it's adding the same object to the list 100x. Is there a way to accomplish this?
def initialize
data = JSON.parse(open(BASE_URL + "markets?vs_currency=usd").read)
i = 0
# looping until we hit the end of the list. adding them all as objects.
while i < data.length
#id = data[i]["id"].to_s
#name = data[i]["name"].to_s
#symbol = data[i]["symbol"].to_s
#price = data[i]["current_price"].to_s
#price_movement_24h = data[i]["price_change_percentage_24h"].to_s
#market_cap = data[i]["market_cap"].to_s
##market << self
i += 1
end
end
This gives me the same object added to the ##market list 100x.
=> [#<Market:0x0000561b3f853f30
#id="iostoken",
#market_cap="43969067",
#name="IOST",
#price="0.0036523",
#price_movement_24h="-0.76702",
#symbol="iost">,
#<Market:0x0000561b3f853f30
#id="iostoken",
#market_cap="43969067",
#name="IOST",
#price="0.0036523",
#price_movement_24h="-0.76702",
#symbol="iost">,

Answer 1

I want to start by saying this is very strange Ruby code and not something you'd typically do. That's not meant as an insult, just to say that Ruby devs tend to follow the same or similar guidelines on structuring objects and this chunk of code feels like it's ported from another language.
The issue you're seeing is due to the fact that within the initialize method you're not creating any new objects but instead updating the instance variables and pushing self into a class variable. self is referencing this instance directly which means the class variable array is filling up with references to the same object. If you're adamant on keeping the code the same then you should instead push a duplicate of your object after you've updated the instance variables.
##market << self.dup
This creates a duplicate object that has a different memory address and reference.
If you're looking to write more idiomatic code you'd want to use multiple objects and not rely on class variables at all. If you're not interpolating a variable in a string use single quotes instead of double quotes. Keep object methods simple and focused on specific tasks. These are just a few things Ruby developers consider when writing code, but find what works best for you.
Take something like this for instance:
class Market
attr_accessor :id, :name, :symbol, :price, :price_movement_24h, :market_cap
def initialize(data = {})
#id = data['id'].to_s
#name = data['name'].to_s
#symbol = data['symbol'].to_s
#price = data['current_price'].to_s
#price_movement_24h = data['price_change_percentage_24h'].to_s
#market_cap = data['market_cap'].to_s
end
end
class ImportService
def self.from_api(url)
response = JSON.parse(open(url).read) || []
response.map { |data| Market.new(data) }
end
end
You could then call this as such:
#market_data = ImportService.from_api(BASE_URL + 'markets?vs_currency=usd')

Answer 2

When adding self to the ##market, you should change the code to this
##market << self.dup
However, I don't think it's a good practice to use a class variable here and add self to init an array of object. Instead, you should create a new class (for example MarketImporter)
class Market
attr_accessor :id, :name, :symbol, :price, :price_movement_24h, :market_cap
def initialize(data = {})
#id = data["id"].to_s
#name = data["name"].to_s
#symbol = data["symbol"].to_s
#price = data["current_price"].to_s
#price_movement_24h = data["price_change_percentage_24h"].to_s
#market_cap = data["market_cap"].to_s
end
end
class MarketImporter
attr_accessor :markets
def initialize
data = JSON.parse(open(BASE_URL + "markets?vs_currency=usd").read)
#markets = data.collect { |item| Market.new(item) }
end
end
Then you can init the collection by
MarketImporter.new