Question

是否有任何可表示的示例来覆盖子接口方法？请看以下示例：

# encoding: utf-8

class EngagementUploader < CarrierWave::Uploader::Base

  # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  include CarrierWave::Processing::RMagick
  # include CarrierWave::MiniMagick
  include CarrierWave::ImageOptimizer

  # Choose what kind of storage to use for this uploader:
  # storage :file
  storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted: #{model.name.to_s.underscore}
  def store_dir
    "#{model.class.to_s.pluralize.parameterize}/#{model.id}/"
  end

  process :optimize => [{ quality: 90 }]

  #process :watermark

  #process :blur => [0, 8]

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process :resize_to_fit => [50, 50]
  # end
  # version :large do
  #   process :resize_to_fill => [512, 512]
  # end
  # version :medium do
  #   process :resize_to_fill => [128, 128]
  # end
  # version :small do
  #   process :resize_to_fill => [48, 48]
  # end
  # version :tiny do
  #   process :resize_to_fill => [32, 32]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_white_list
    %w(jpg jpeg gif png)
  end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

  def filename
    if original_filename
      "post-#{secure_token(16)}.#{file.extension}"
    end
  end

  protected
  def secure_token(length=16)
    var = :"@#{mounted_as}_secure_token"
    model.instance_variable_get(var) or model.instance_variable_set(var, SecureRandom.hex(length/2))
  end

  # def watermark
  #   manipulate! do |img|
  #     logo = Magick::Image.read("#{Rails.root}/app/assets/images/watermark.png").first
  #     img = img.composite(logo, Magick::SouthEastGravity, 15, 15, Magick::OverCompositeOp)
  #   end
  # end

end

Answer 1

如果I1和I2都没有实现foo()（而且我们知道它们不适用于Java 8之前的版本），那么它就不会出现这种情况。让I2再次声明foo()是有意义的。它等同于I2只是一个扩展I1的空接口。

但是，在Java 8中，有一些默认方法，允许您为接口方法提供默认实现。您可以在foo()中使用I1的一个默认实现，在foo()中使用I2的默认实现。在这种情况下，I2 foo()可以覆盖I1 foo()。

覆盖子接口方法

1 个答案: