How to know if an image has been uploaded or not? - Paperclip

问题

do you know if is there a method to know if the image has been uploaded?

I mean, i have a Foo_Class, and this class can have an attached image, but its presence is not necessary. Is there a way to know if a particular instance of that class have the image or not?

Thanks!

回答1:

When you added Paperclip to your model you added paperclip specific rows, mine are

cover_file_name
cover_content_type
cover_file_size
cover_updated_at

Then I check whether it is nil or not

 Foo_Class.cover_file_name.nil? 

回答2:

If foo.image? returns true, then file uploaded.

回答3:

I think that the proper solution is to use the file? method.

foo.image.file?

http://rdoc.info/github/thoughtbot/paperclip/Paperclip/Attachment#file%3F-instance_method

using exists? will do a request to the server to check if the file is there, which can be quite slow, especially if it's on a different server or on S3.

using foo.image_file_name.nil? is probably the same as file? under the covers, but ou don't want to dependant on the implementation of paperclip, which could someday change.

回答4:

If this is in my model

has_attached_file :avatar, :styles => {:logo => "230x50>", :card_image => "180x50>"}

You can check if the image is uploaded for a user i.e @user

<%= @user.avatar.exists? %>

This will return boolean value.

回答5:

Suppose you want to check the presence of attachment(image) for the 1st row in Foo model:

image_present = Foo.first.image?

This returns true if the attachment is present.

来源：https://stackoverflow.com/questions/5593829/how-to-know-if-an-image-has-been-uploaded-or-not-paperclip