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Standard steps

The following are built-in standard steps, provided to accomplish common tasks.

Never use new in plan resolvers

Remember to use the step function rather than the underlying step class; this allows for more ergonomic APIs and iteration of the produced steps without breaking changes to your plan resolvers.

As a general rule of thumb, your plan resolvers should never contain the new keyword.

These standard steps are built into the grafast module and can be used as a foundation for your project, and are often sufficient for a schema's needs — particularly when integrating with an existing business logic layer.

Loading data​

  • loadOne: like an more powerful DataLoader.load — batch loading of single values
  • loadMany: like a more powerful DataLoader.load — batch loading of lists of values

Forming objects and lists​

  • list: accepts a tuple (list) of steps and turns it into a single step that yields a list of the underlying steps' values
  • object: accepts an object with string keys and step values, and turns it into a step that yields an object where the keys are retained and values are those yielded from the underlying steps
  • remapKeys: returns step that results in an object made up of the given renamed keys and values from another object step (useful during optimization when a step inlines its work into an ancestor and wishest to replace itself with access to specific properties therein)

Operating on lists​

  • first: returns a step representing the first entry from a list
  • last: returns a step representing the last entry from a list
  • reverse: returns a step representing a new list with reverse order
  • filter: returns a step representing only the entries in a list that satisfy a callback
  • groupBy: accepts a single dimensional list plan and a mapper that returns a grouping key. Returns a step that yields a Map where the keys are the grouping keys and the values are lists of the original entries that match these grouping keys
  • each: accepts a step representing a list and returns a step representing the same list but where traversal of the list will result in the list item being transformed by the given (plan-time) callback

Utility​

  • constant: creates a step representing the raw JavaScript value (number, string, etc) passed in
  • access: returns a step representing accessing the property at the given path for each runtime value
  • lambda: returns a step representing transforming each value with the given (execution-time) callback
  • multistep: accepts a step, step tuple, or step map; returns a single step with the same shape

GraphQL​

  • context: returns a step representing the GraphQL contextValue
  • connection: wraps a step representing a list with connection-related capabilities such as pagination
  • Also: Node-related functions (regarding the GraphQL Global Object Identification spec)

Realtime​

  • listen: Subscribes to the given pubsubOrPlan to get realtime updates on a given topic (topicOrPlan), mapping the resulting event via the itemPlan callback.

Flow control​

See Flow control for a conceptual overview.

  • inhibitOnNull: inhibit dependent work when an input is null-ish
  • assertNotNull: raise an error when a value is unexpectedly null-ish
  • trap: turn inhibited or errored values back into usable data