Paperclip is an easy-to-use file upload gem released by Thoughtbot. It provides several validations out of the box like validation on size (as in file size) of the attachment, if the attachment is present or not and so on. However, it does not have any validations on the dimensions of the file because sometimes you have to ensure the file is the correct dimension to avoid any design disasters.
To validate dimensions, one needs two things, namely:
1) Dimension of the file that is being uploaded and
2) Dimensions to validate against or the desired dimensions
One tutorial, I found particular useful in my quest is by Roberto Soares. It doesn’t exactly touch on the topic I am talking about here but it does point me in the right direction. He gives code to calculate the dimension of the file being uploaded, in case you would like to save the height and width of the file in the model.
How is my problem different from Roberto’s?
1) I do not want to save the height and width of the file in the database.
2) My desired dimensions are already stored in a different model, i.e. I do not need to define it explicitly like other validations, such as validates_length_of :name, :within => 2..10
So, it is a particular sort of situation. Without any more discussions, here’s the code:
class Dummy < ActiveRecord::Base
has_attached_file :photo
def validate
temp_file = photo.queued_for_write[:original] #get the file that is being uploaded
dimensions = Paperclip::Geometry.from_file(temp_file)
if (dimensions.width > desired_width) || (dimensions.height > desired_height)
errors.add("photo_size", "must be image size #{desired_width}x#{desired_height}.")
end
end
def desired_height
# retrieve it from a different model
end
def desired_width
# retrieve it from a different model
end
Key thing to note, is the @queued_for_write attribute that is defined on Attachment class within Paperclip. This keeps hold of the original file that is being uploaded, which I then retrieve to get the dimensions. I simply compare the height and width in the validate method that gets called before save. This does work but it’s a dirty hack and is impossible to reuse. Therefore, I am going to try and extract it out and make it more reusable. Stay tuned for it.
Please Note: This is just a monkey-patch and will increase your technical debt. Use it carefully, with an intention to refactor it as soon as possible.
In my previous post, I mentioned a way of validating the size of the attachment and I did warn readers that it is a monkey-patch and it needs serious refactoring.
Big refactoring is a result of several small ones and that’s exactly what I have done here. I have extracted the code out and it looks much neater now. As a result, I have reduced my technical debt and in the process gained a better understanding of Paperclip.
Objective:
1. Make code reusable, probably extract it out and then use Ruby’s magic to add it straight to Paperclip. So, that next time I can just use it without doing all the extra work.
2. Make the existing code neat.
3. To retrieve the width and height of the attachment.
This is where we left the code last time:
class Dummy < ActiveRecord::Base
has_attached_file :photo
def validate
temp_file = photo.queued_for_write[:original] #get the file that is being uploaded
dimensions = Paperclip::Geometry.from_file(temp_file)
if (dimensions.width > desired_width) || (dimensions.height > desired_height)
errors.add("photo_size", "must be image size #{desired_width}x#{desired_height}.")
end
end
def desired_height
# retrieve it from a different model
end
def desired_width
# retrieve it from a different model
end
Above, I have used @queued_for_write to retrieve the attachment object but if this code changes in Paperclip and I am using it in, let us say 5 different places, I will have to fix it in all those places. I just don’t want to come back and change the code every time Paperclip changes anything. Therefore, this is plain wrong. Similarly, if the Paperclip::Geometry’s API changes, I will have to endure the same painful process yet again. Therefore, it becomes essential to extract this code out into its own module and then it’s all in one place. Right, so I created a module, as below:
module Paperclip
module Dimension
# calculates width using processor
def width_of name
return 0 unless path(name)
Geometry.from_file(path(name)).width.to_i
end
# calculates height using processor
def height_of name
return 0 unless path(name)
Geometry.from_file(path(name)).height.to_i
end
#path to the attachment
def path name
attachment_for(name).queued_for_write[:original]
end
end
end
I am instead using a method attachment_for within Paperclip. For example, if you have code like:
has_attached_file :photo
then, you can do something like:
attachment_for :photo
to get hold of the attachment object. But bear in mind, has_attached_file is a class method where as attachment_for is an instance method (I can’t really explain the difference here but the fact is they can’t be used in a similar way). This allows me to change the code in my model to something like this:
class Dummy < ActiveRecord::Base
has_attached_file :photo
def validate
if width_of(:photo) > desired_width || height_of(:photo) > desired_height
errors.add("photo_size", "must be image size #{desired_width}x#{desired_height}.")
end
end
def desired_height
# retrieve it from a different model
end
def desired_width
# retrieve it from a different model
end
Wow! That is clean and has the same syntax as has_attached_file. I don’t need to indulge in Paperclip’s nitty gritty. It’s in a different module. But you can’t run this code just yet. Because, it’s not hooked into my application yet. If you do run it, you should see NoMethodError on width_of. In order to hook this code up into our application, add the module to a file, let us name it, paperclip.rb and put it inside app_root/config/initializers/.
So, when the app starts up it will load this file but this module is nothing without the support of actual Paperclip. Therefore, to hook it into Paperclip, we will add the following line at the bottom and the module in it’s final state would look something like this:
module Paperclip
module Dimension
# calculates width using processor
def width_of name
return 0 unless path(name)
Geometry.from_file(path(name)).width.to_i
end
# calculates height using processor
def height_of name
return 0 unless path(name)
Geometry.from_file(path(name)).height.to_i
end
#path to the attachment
def path name
attachment_for(name).queued_for_write[:original]
end
end
end
Paperclip::InstanceMethods.send(:include, Paperclip::Dimension)
I am including our custom module inside Paperclip::InstanceMethods, which gets called when has_attached_file is invoked from within the model class and ensures all the instance methods are available to our model class.
Now, if you run it. It will work like a charm. By just adding this code to your initializers you can simply retrieve the width and height of the attachment. Here’s the gist of the file, if you need it.
I hope it helps and for anyone interested, please go ahead and create a validator for dimensions just like we have one for size.
Safari 5 is awesome and one thing that sticks out is the Reader feature. It basically identifies some pages, for example: news pages on BBC, and allows user to produce a better, enhanced page with same text but much readable than before and devoid of any ads or pictures. But it fails badly here. If you are on Safari 5 and click the link and then click the READER button in the address bar, you’ll agree with me.
Well, apart from one odd example, I think it works brilliant. I just thought I will point it out that it should identify the code blocks with pre or code tags and format them accordingly.
Majority of us have seen this dreadful error after running rake:gems:unpack or a similar command to register gems with the application.
config.gem: Unpacked gem clearance-0.8.8 in vendor/gems has no specification file. Run 'rake gems:refresh_specs' to fix this.
I was under the impression that this happens due to some bug in rails gem dependency management and never expected the same to happen with Bundler. Unfortunately, I was wrong. Just yesterday, I had this error and it’s one of those things that doesn’t really stop your app from working but is very annoying.
There is a fix on Stack Overflow but it might not work if you are using bundler. The command to use remains the same but it needs to be slightly modified. Here are the steps:
This assumes that you get this error with clearance.
With bundler the gem files are actually stored in the vendor/cache directory. specification is a gem command that extracts a .specification file from gem file. Here’s full explanation of it.
Time selection via web has always been those grey areas where one does not really find good solutions. With the advent of Jquery, there are plethora of date selection javascripts out there. However, time selection has not received similar treatment. After much searching I found two solutions. The first one was very fancy but depended heavily on the Jquery Widget and with custom ui stuff rewritten in recent versions, it simply did not work with newest custom-ui scripts.
The second solution was simple and straight-forward but laden with bugs. However, a bit of hacking yielded a good working solution but it was still lacking something important and essential i.e. Tests. After a bit of googling, I zeroed on JSSpec as the testing framework. QUnit is at par with JSSpec but I quite like the RSpec way of testing and JSSpec emulates that for javascript.
Testing is hard. No doubts about it. But testing javascript is a completely different ball game. It is easy and quite fun, once you get the hang of it but initially it is just confusing. I had problems in setting up the test cases, ensuring the requisites are there. For example: if we are testing weather an input box slides out on a link click then we need to make sure that an input box is there. I know it sounds easy but when it comes down to writing specs, mind goes completely blank. Anyways, here’s the link to jquery-timepicker. Go and check it out.