如何在 Ruby 中向现有 JSON 对象添加新的键/值对

Question

How could I append a new key/value pair to an existing JSON object in Ruby?

My output is:

{
    "2d967df3-ee07-4e40-8f65-7bbff59bbb7e": {
        "name": "Book1",
        "author": "Author1"
    }
}

I want to achieve something like this when I add a new key/value pair:

{
    "2d967df3-ee07-4e40-8f65-7bbff59bbb7e": {
        "name": "Book1",
        "author": "Author1"
    },
    "c55a3632-9bed-4a41-ae40-c1abfe0f332a": {
        "name": "Book2",
        "author": "Author2"
    }
}

This is my method to write to a JSON file:

def create_book(name, author)
    tempHash = {
        SecureRandom.uuid => {
            "name" => name,
            "author" => author
            }
    }

    File.open("./books/book.json","w") do |f|
      f.write(JSON.pretty_generate(tempHash))
    end
end

To clarify, I need to add a second entry to the original file. I tried using append ( << ), and that's where my code fails:

file = File.read("./books/book.json") 
data_hash = JSON.parse(file) 
newJson = data_hash << tempHash

Answer 1

How could I append a new key/value pair to existing JSON object in Ruby?

If you want to add it to an existing file then you should read the JSON first, extract data from it, then add a new hash to an array.

Maybe something like this will solve your problem:

def create_book(name, author)
  tempHash = {
  SecureRandom.uuid => {
    "name" => name,
    "author" => author
    }
  }

  data_from_json = JSON[File.read("./books/book.json")]
  data_from_json = [data_from_json] if data_from_json.class != Array
  File.open("./books/book.json","w") do |f|
    f.write(JSON.pretty_generate(data_from_json << tempHash))
  end
end

There are also some other ways like manipulating the JSON as a common string but for safety you should extract the data and then create a new JSON file.

Answer 2

If you need the new key/value pair to be in the same JSON element as the previous data, instead of shoveling ( << ) the hashes together, merge them.

Additionally this can allow you to put the new key/value pair in the start of the element or in the end, by flipping which hash you merge first.

So, take Maxim's solution from Apr 14 '15, but modify to merge the two hashes together.

  data_from_json = JSON[http://File.read("./books/book.json")]
  File.open("./books/book.json","w") do |f|
    f.write(JSON.pretty_generate([data_from_json.merge(tempHash)])
  end