Output Filters



The dig output filter is used to dig into a returned data set and return a subset of the structure. This is particularly useful if the end data source encapsulates the required data under some data structure that is not wanted. For example, imagine a data source that returns key value pairs under a nested hash of “documents” and “settings”, eg:

  "document": {
    "settings": {
      "foo": "bar"

If we are only interested in the settings hash we can tell Jerakia to dig into the result and return just the subset that we need. The dig output_filter takes an array as an argument, each element of the array corresponds to a key in the hash to dig through. So, to always return the subset of data under settings in this scenario we can acheieve this by using the following filter in the lookup

lookup :default do
  output_filter :dig, [ 'document', 'settings' ]

With this filter in place, the returned data in the above example would now be;

{ "foo": "bar" }

See the Data Digging section of the HTTP datasource documentation for a more real world example of using the dig output filter