params.md

Params

This extension adds a WebPipe::Conn#params method which returns request parameters as a Hash. Then, any number of transformations on it can be configured.

When no transformations are configured, #params returns GET and POST parameters as a hash:

# http://www.example.com?foo=bar
conn.params # => { 'foo' => 'bar' }

You can configure a stack of transformations to be applied to the parameter hash. For that, we lean on dry-transformer gem (you have to add it yourself to your Gemfile). All hash transformations in dry-transformer are available by default.

Transformations must be configured under :param_transformations key:

require 'web_pipe'

WebPipe.load_extensions(:params)

class MyApp
  incude WebPipe
  
  plug :config, WebPipe::Plugs::Config.(
    param_transformations: [:deep_symbolize_keys]
  )

  plug(:this) do |conn|
    # http://www.example.com?foo=bar
    conn.params => # => { foo: 'bar' }
    # ...
  end
end

Extra needed arguments can be provided as an array:

# ...
plug :config, WebPipe::Plugs::Config.(
  param_transformations: [
    :deep_symbolize_keys, [:reject_keys, [:zoo]]
  ]
)

plug(:this) do |conn|
  # http://www.example.com?foo=bar&zoo=zoo
  conn.params => # => { foo: 'bar' }
  # ...
end
# ...

Custom transformations can be registered in WebPipe::Params::Transf transproc register:

fake = ->(_params) { { fake: :params } }
WebPipe::Params::Transf.register(:fake, fake)

# ...
plug :config, WebPipe::Plugs::Config.(
  param_transformations: [:fake]
)

plug(:this) do |conn|
  # http://www.example.com?foo=bar
  conn.params => # => { fake: :params }
  # ...
end
# ...

Your own transformation functions can depend on the WebPipe::Conn instance at the moment of calling #params. Those functions must accept the connection struct as its last argument:

add_name = ->(params, conn) { params.merge(name: conn.fetch(:name)) }
WebPipe::Params::Transf.register(:add_name, add_name)

# ...
plug :config, WebPipe::Plugs::Config.(
  param_transformations: [:deep_symbolize_keys, :add_name]
)

plug(:add_name) do |conn|
  conn.add(:name, 'Alice')
end

plug(:this) do |conn|
  # http://www.example.com?foo=bar
  conn.params => # => { foo: :bar, name: 'Alice' }
  # ...
end
# ...

Finally, you can override the configured transformations injecting another set at the moment of calling #params:

# ...
plug :config, WebPipe::Plugs::Config.(
  param_transformations: [:deep_symbolize_keys]
)

plug(:this) do |conn|
  # http://www.example.com?foo=bar&zoo=zoo
  conn.params([:reject_keys, ['zoo']]) => # => { 'foo' => 'zoo' }
  # ...
end
# ...