Appending the data in JSON file using Ruby

Question

I am trying to write/append some data in a JSON file using ruby. I am facing issues while writing data in JSON file in proper format. I have created and stored my values in temphash. I want to append the content of temphash in existing JSON file. I am doing it in following way:

 tempHash = {"Group_Name" => @GroupName, "Group_Logo_Code" => @GroupLogoCode }

 json = File.read('public/group.json')
 secondJsonArray = JSON.parse(json)
 secondJsonHash = Hash[*secondJsonArray]

 jsonHash = []  
 jsonHash << secondJsonHash
 jsonHash << tempHash      

 File.open("public/group.json","w") do |f|
  f.puts JSON.pretty_generate(jsonHash)
 end 

This is creating malformed JSON. I am not getting the JSON in expected format

Below is what I expect:

[ 
 {
  "Group_Name": "Group Name",
  "Group_Logo_Code": "Group Logo code"
 },
 {
  "Group_Name": "Group Name",
  "Group_Logo_Code": "Group Logo code"
 },
 {
  "Group_Name": "Group Name",
  "Group_Logo_Code": "Group Logo code"
 },
]    

Below is what I am getting:

[
  {
    "{\"{\\\"Group_Name\\\"=>\\\"Group Name\\\", \\\"Group_Logo_Code\\\"=>\\\"Group Logo code\\\"}\"=>{\"Group_Name\"=>\"Group Name\", \"Group_Logo_Code\"=>\"Group Logo code\"}}": {
  "Group_Name": "Group Name",
  "Group_Logo_Code": "Group Logo code"
    }
   },
  {
    "Group_Name": "Group Name",
    "Group_Logo_Code": "Group Logo code"
  }
]

Please let me know if there is any better way to do this. Can anyone please help me resolve this issue. Thanks in advance.

Answer 1

Uri Agassi's code is perfect, but I thought to explain what went wrong in the OP code.

The Hash[] expects an array of key, value pairs (either as separate arguments or an array of arrays):

Hash[:a, 1, :b, 2]        # => {:a=>1, :b=>2}
Hash[[[:a,1], [:b,2]]]    # => {:a=>1, :b=>2}

But the original JSON contained Array of Hashes which gets parsed into corresponding Ruby objects as in the simplified case:

[{:a => 1}, {:b => 2}]

When you use the Ruby splat operator * on the above array:

Hash[ *[{:a => 1}, {:b => 2}] ]

You efectively provide separate hashes as a key-value pair to the Hash constructor:

Hash[ {:a => 1}, {:b => 2} ]  # => {{:a=>1} => {:b=>2}}

So, essentially, you got what you asked for: you turned a array of hashes into a hash of hashes and then you added that to a blank array and topped up with another hash.

Correct solution

Just to make the original code work with minimal changes (but still take a look at Uri's solution):

tempHash = {"Group_Name" => @GroupName, "Group_Logo_Code" => @GroupLogoCode }

json = File.read('public/group.json')
secondJsonArray = JSON.parse(json)

secondJsonArray << tempHash

File.open("public/group.json","w") do |f|
  f.puts JSON.pretty_generate(secondJsonArray)
end

Answer 2

It seems that you are doing much too much in this code - why are you trying to convert the array to a hash? Leave it as an array:

tempHash = {"Group_Name" => @GroupName, "Group_Logo_Code" => @GroupLogoCode }

json = File.read('public/group.json')

File.open("public/group.json","w") do |f|
  f.puts JSON.pretty_generate(JSON.parse(json) << tempHash)
end