Rails 3.2: Replace null values with empty string from json serialization

问题

I am using Rails 3.2 serialization to convert ruby object to json.

For Example, I have serialized ruby object to following json

{
  "relationship":{
    "type":"relationship",
    "id":null,
    "followed_id": null
  }
}

Using following serialize method in my class Relationship < ActiveRecord::Base

def as_json(opts = {})
  {
   :type        => 'relationship',
   :id          => id,
   :followed_id => followed_id
  }
end

I need to replace null values with empty strings i.e. empty double quotes, in response json.

How can I achieve this?

Best Regards,

回答1:

Probably not the best solution, but inspired by this answer

def as_json(opts={})
  json = super(opts)
  Hash[*json.map{|k, v| [k, v || ""]}.flatten]
end

-- Edit --

As per jdoe's comment, if you only want to include some fields in your json response, I prefer doing it as:

def as_json(opts={})
  opts.reverse_merge!(:only => [:type, :id, :followed_id])
  json = super(opts)
  Hash[*json.map{|k, v| [k, v || ""]}.flatten]
end

回答2:

I don't see the problem here. Just make it via || operator:

def as_json(opts = {})
  {
   :type        => 'relationship',
   :id          => id || '',
   :followed_id => followed_id || ''
  }
end

回答3:

using below method you will get modified hash or json object. it will replace blank string with nill. need to pass the hash in parameter.

def json_without_null(json_object)
  if json_object.kind_of?(Hash)
    json_object.as_json.each do |k, v|
      if v.nil?
        json_object[k] = ""
      elsif  v.kind_of?(Hash)
        json_object[k] = json_without_null(v)
      elsif v.kind_of?(Array)
        json_object[k] = v.collect{|a|  json_without_null(a)}
      end
    end
  end
  json_object
end

来源：https://stackoverflow.com/questions/10811628/rails-3-2-replace-null-values-with-empty-string-from-json-serialization