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A set of transformations that can be applied to a blob to create a variant. This class is exposed via the ActiveStorage::Blob::Representable#variant method and should rarely be used directly.

In case you do need to use this directly, it's instantiated using a hash of transformations where the key is the command and the value is the arguments. Example:

ActiveStorage::Variation.new(resize_to_fit: [100, 100], monochrome: true, trim: true, rotate: "-90")

The options map directly to ImageProcessing commands.

Methods
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Attributes
[R] transformations
Class Public methods
decode(key)

Returns a Variation instance with the transformations that were encoded by encode.

# File activestorage/app/models/active_storage/variation.rb, line 31
def decode(key)
  new ActiveStorage.verifier.verify(key, purpose: :variation)
end
encode(transformations)

Returns a signed key for the transformations, which can be used to refer to a specific variation in a URL or combined key (like ActiveStorage::Variant#key).

# File activestorage/app/models/active_storage/variation.rb, line 37
def encode(transformations)
  ActiveStorage.verifier.generate(transformations, purpose: :variation)
end
new(transformations)
# File activestorage/app/models/active_storage/variation.rb, line 42
def initialize(transformations)
  @transformations = transformations
end
wrap(variator)

Returns a Variation instance based on the given variator. If the variator is a Variation, it is returned unmodified. If it is a String, it is passed to ::decode. Otherwise, it is assumed to be a transformations Hash and is passed directly to the constructor.

# File activestorage/app/models/active_storage/variation.rb, line 19
def wrap(variator)
  case variator
  when self
    variator
  when String
    decode variator
  else
    new variator
  end
end
Instance Public methods
key()

Returns a signed key for all the transformations that this variation was instantiated with.

# File activestorage/app/models/active_storage/variation.rb, line 57
def key
  self.class.encode(transformations)
end
transform(file, format: nil, &block)

Accepts a File object, performs the transformations against it, and saves the transformed image into a temporary file. If format is specified it will be the format of the result image, otherwise the result image retains the source format.

# File activestorage/app/models/active_storage/variation.rb, line 50
def transform(file, format: nil, &block)
  ActiveSupport::Notifications.instrument("transform.active_storage") do
    transformer.transform(file, format: format, &block)
  end
end