How to parse array of hashes (strings)

Question

I have the following array:

["{\"id\":1,\"name\":\"A\"}", "{\"id\":20,\"name\":\"B\"}"]

I get this array from redis and I need to iterate and access id and name keys. I really need to call JSON.parse in every iteration ?

How can I iterate and display data ?

"I really need to call JSON.parse in every iteration?" - on every element, yes. — Sergio Tulentsev
– Sergio Tulentsev, Commented Feb 16, 2018 at 13:24
like this? <% visitors.each do |v| %> <% visitor = JSON.parse(v) %> — Joao Silva
– Joao Silva, Commented Feb 16, 2018 at 13:26
This is one way to do this, yes. I'd prefer to not bloat my views with unnecessary logic, and move data preparation elsewhere (controller, for example) — Sergio Tulentsev
– Sergio Tulentsev, Commented Feb 16, 2018 at 13:27
yes I did this on a cell: def visitors @options[:visitors].map { |visitor| JSON.parse(visitor) } end — Joao Silva
– Joao Silva, Commented Feb 16, 2018 at 13:31
"I get this array from redis" – how is it stored in Redis, as a list? — Stefan
– Stefan, Commented Feb 16, 2018 at 14:11

Martin · Accepted Answer · 2018-02-16 14:55:31Z

1

First, nothing wrong with a loop:

arr = ["{\"id\":1,\"name\":\"A\"}", "{\"id\":20,\"name\":\"B\"}"]
arr.map {|raw| JSON.parse(raw) }

Now, if for any reason you want to avoid the loop, here is some fun option:

arr = ["{\"id\":1,\"name\":\"A\"}", "{\"id\":20,\"name\":\"B\"}"]
JSON.parse "[#{arr.join(",")}]"

So: join the array with ",", making a string that we put between "[]" - this transform your list of JSON encoded values into a single JSON encoded array.

This being said, again - nothing wrong with a loop.

answered Feb 16, 2018 at 14:55

Martin

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3 Comments

peter Over a year ago

good solution Martin, tried that but without the surrounding [] it failed

Martin Over a year ago

Just tried the code in my IRB with your exact example, looks to work:

peter Over a year ago

iaa you misunderstood, your example works +1 (otherwise wouldn't be good :), I tried it the same way and it failed because of..

peter · Accepted Answer · 2018-02-16 15:23:03Z

On your question if you need to do this with a map method you got the answer allready in the comments and the alternative from Martin.

Here is a way to separate the logic from your view like Sergio suggests

Somewhere in your controller, model or helper file

class Visitor
  require 'json'
  def initialize string
    hash = JSON.parse(string)
    @id   = hash["id"]
    @name = hash["name"]
  end

  def to_s
    "#{@id}: #{@name}"
  end
end

class Visitors
  include Enumerable

  @@visitors = []
  def initialize array
    array.map{|visitor| @@visitors << Visitor.new(visitor)}
  end

  def each
    @@visitors.map{|visitor| yield visitor}
  end
end


array = ["{\"id\":1,\"name\":\"A\"}", "{\"id\":20,\"name\":\"B\"}"]
visitors =  Visitors.new(array)

And in your view

visitors.each do |visitor|
  <%=visitor%>
end

# 1: A
# 20: B

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