This can cut down on processing cost. Occasionally you want to restrict the creation of versions on certain properties within the model or based on the picture itself. The model variable points to the instance object the uploader is attached to. For performance reasons, it is often useful to create versions from existing ones instead of using the original file. If your uploader generates several versions where the next is smaller than the last, it will take less time to generate from a smaller, already processed image.
Often you'll notice that uploaded files disappear when a validation fails. CarrierWave has a feature that makes it easy to remember the uploaded file even in that case. In Rails, this would look like this:. It might be a good idea to show the user that a file has been uploaded, in the case of images, a small thumbnail would be a good indicator:. If you want to remove a previously uploaded file on a mounted uploader, you can easily add a checkbox to the form which will remove the file when checked.
Your users may find it convenient to upload a file from a location on the Internet via a URL. CarrierWave makes this simple, just add the appropriate attribute to your form and you're good to go:. If you're using ActiveRecord, CarrierWave will indicate invalid URLs and download failures automatically with attribute validation errors.
This option is effective when the remote destination is unstable. In many cases, especially when working with images, it might be a good idea to provide a default url, a fallback in case no file has been uploaded.
You might come to a situation where you want to retroactively change a version or add a new one. This uses a naive approach which will re-upload and process the specified version or all versions, if none is passed as an argument.
When you are generating random unique filenames you have to call save! Calling save! To avoid this, scope the records to those with images or check if an image exists within the block. If you're using ActiveRecord, recreating versions for a user avatar might look like this:.
CarrierWave has a broad range of configuration options, which you can configure, both globally and on a per-uploader basis:.
If you want CarrierWave to fail noisily in development, you can change these configs in your environment file:. It's a good idea to test your uploaders in isolation. In order to speed up your tests, it's recommended to switch off processing in your tests, and to use the file storage. In Rails you could do that by adding an initializer with:. Remember, if you have already set storage :something in your uploader, the storage setting from this initializer will be ignored.
If you need to test your processing, you should test it in isolation, and enable processing only for those tests that need it. Processing can be enabled for a single version by setting the processing flag on the version like so:. If you want to use fog you must add in your CarrierWave initializer the following lines.
Ensure you have it in your Gemfile:. For the sake of performance it is assumed that the directory already exists, so please create it if it needs to be. Here's a full example:. That's it! Note : for Carrierwave to work properly it needs credentials with the following permissions:. Fog is used to support Rackspace Cloud Files. You'll need to configure a directory also known as a container , username and API key in the initializer. For the sake of performance it is assumed that the directory already exists, so please create it if need be.
You can optionally include your CDN host name in the configuration. This is highly recommended, as without it every request requires a lookup of this information. Fog is used to support Google Cloud Storage. You'll need to configure a directory also known as a bucket and the credentials in the initializer. You can still use the CarrierWave::Uploader url method to return the url to the file on Google.
Since Carrierwave doesn't know which parts of Fog you intend to use, it will just load the entire library unless you use e. If you prefer to load fewer classes into your application, you need to load those parts of Fog yourself before loading CarrierWave in your Gemfile.
Beware that this specific require is only needed when working with a fog provider that was not extracted to its own gem yet. A list of the extracted providers can be found in the page of the fog organizations here. If you're uploading images, you'll probably want to manipulate them in some way, you might want to create thumbnail images for example. CarrierWave comes with a small library to make manipulating images with RMagick easier, you'll need to include it in your Uploader:.
You can set a process callback, which will call that method any time a file is uploaded. There is a demonstration of convert here. Convert will only work if the file has the same file extension, thus the use of the filename method.
Check out the manipulate! This allows you to have the power of ImageMagick without having to worry about installing all the RMagick libraries. Currently, the MiniMagick carrierwave processor provides exactly the same methods as for the RMagick processor. See the documentation for CarrierWave::Compatibility::Paperclip for more details.
The Active Record validations use the Rails i18n framework. Add these keys to your translations file:. The carrierwave-i18n library adds support for additional locales. By default, CarrierWave copies an uploaded file twice, first copying the file into the cache, then copying the file into the store. For large files, this can be prohibitively time consuming. By default, mounting an uploader into an ActiveRecord model will add a few callbacks.
For example, this code:. If you want to skip any of these callbacks eg. In addition to the ActiveRecord callbacks described above, uploaders also have callbacks. Uploader callbacks can be before or after the following events:. The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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Example: Step 1 Create a Rails application called upload. Click on New Resume. Click on Save button.
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