How can I get url for paperclip image in to_json

I have a model that uses paperclip like this:

has_attached_file :avatar, :styles => { :large => "100x100>" , :medium => "50x50>", :small => "20x20>" },  :default_url => '/images/missing-owner_:style.png'

I'm exporting this model with to_json method and I want to export the image url so I could use it in javascript.

I know I can access the url like this in the view:

<%= image_tag model.avatar.url(:medium) %>

But How c开发者_如何学Can I do the same in the to_json method.

I have some like this:

respond_to do |format|
   render :json => @model.to_json(:only => [:id,:name,:homephone,:cellphone])
end

I believe the easiest way for you to accomplish this will be to create a method in your object to return the avatar URL.

class Model < ActiveRecord::Base
    ...

    def avatar_url
        avatar.url(:medium)
    end

    ...
end

This will then allow you to use the methods option when calling to_json with a simple method that does not require any parameters:

respond_to do |format|
   render :json => @model.to_json(:only => [:id,:name,:homephone,:cellphone], :methods => [:avatar_url])
end

Which should yield you an output along these lines:

{"id" => 1, "name" => "Cool model", "homephone" => 1234567890, "cellphone" => 0987654321, "avatar_url" => "www.coolsite.com/this_avatars_path"}

See these for reference:

Ruby to_json :methods arguments

http://apidock.com/rails/ActiveRecord/Serialization/to_json

show controller for display image json

localhost:3000/cities/1.json

respond_to do |format|
  format.html
  format.json { render :json => @model.to_json(:methods => [:model_url]) }
end