defaults

@thing-description-playground/DEFAULTS

The package adds/removes defaults according to the Thing Description (TD) specification for every property with a default that is not filled with a value. Currently using this version of the TD specification. It is part of the Playground, you can find more information about the Playground here.

License

Licensed under the MIT license, see License.

Usage

You can use this package to integrate TD default value adding/removing in your application.

• Install this package via NPM (npm install @thing-description-playground/defaults) (or clone repo and install the package with npm install)

• Node.js or Browser import:

  • Node.js: Require the package and use the functions

  const { addDefaults, removeDefaults } = require("@thing-description-playground/defaults");

  • Browser: Import the tdDefaults object as a global by adding a script tag to your html (and optionally declare the variables without namespace).

  <script src="./node_modules/@thing-description-playground/add_defaults/dist/web-bundle.min.js"></script>

  const addDefaults = tdDefaults.addDefaults;
  const removeDefaults = tdDefaults.removeDefaults;

• Now you can call the add/remove defaults function to extend/reduce a TD object.

  addDefaults(td);
  removeDefaults(td);

  You can find usage examples in the tests folder, or the web and cli packages.

Documentation

• How it works:
  The algorithm shipped with package basically tries to check all possible place (in terms of object hierachy e.g. td.properties.temperature) type combinations (lines 1 - 3). A type refers to one objects default values (e.g. form -> op: application/json). All existing combinations in the given TD, are then passed to a handle function (lines 4, 5). Since there can be nested places of type DataSchema (e.g. if one DataSchema includes another by using oneOf), these need to be handled recursively (lines 6 - 10).
  The handle function (lines 13 - 20) checks the place & type combinations in the given TD, depending on whether it should add or remove default values:

  • add: If the default value(s) corresponding to the place type combination is/are not defined in the current TD, if this is true it adds the default value(s) (lines 14 - 16).
  • remove: If the place type combination value(s) equal the default value(s), if this is true it removes the value(s) (lines 17 - 19).

• pseudocode:

  #1  | checkAllPossibleDefaultValuePlaces(td) {
  #2  |   for (every type of defaultTypes)
  #3  |     for (every place of possiblePlaces[type])
  #4  |       if (td[place] !== undefined)
  #5  |         handle(td[place], type)
  #6  |       if (type == "DataSchema")
  #7  |         currentPlace = td[place]
  #8  |         while (hasRecursiveElements(currentPlace))
  #9  |           handle(currentPlace, "DataSchema")
  #10 |           currentPlace = currentPlace[recursion]
  #11 | }
  #12 |
  #13 | handle(object, type) {
  #14 |   if (mode == "add")
  #15 |     if (object[type] == undefined)
  #16 |       object[type] = defaultTable[type]
  #17 |   if (mode == "remove")
  #18 |     if (object[type] == defaultTable[type])
  #19 |       delete object[type]
  #20 | }