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Single Update Rule configuration#

These rules declare which Observers to update when a Subject changes.

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const updateRuleConfiguration = {
    name: 'fieldName',
    update: [],  // Names of the Observers to update when the Subject changes
    additionalData: [], // Names of other fields whose values go in the Update Data
    externalData: (data, subjectName) => { } // Function which returns external data to add to the Update Data
};

name*#

The name of the Subject.

update#

The names of the Observers to update when the Subject changes. Their own Observers are cleared on cascade, since their value is no longer valid.

Update Rules can't form a cycle: a field can't be an Observer of itself, directly or through other fields. makeForm throws Update rules form a cycle: a → b → a when they do.

additionalData#

The names of other fields whose values are read and added to the Update Data.

externalData (data, subjectName)#

A function to add to the Update Data other data, external to the form (e.g. a timestamp).

Parameters

  • {object} data: the Update Data collected so far, with the Subject's value and the additionalData values
  • {string} subjectName: the name of the Subject

Returns

  • {object} An object with external data values (key-value format)

Update Data#

The data an Observer receives for an update, keyed by field name: the Subject's value, plus the values of the additionalData fields and the object returned by externalData.

Field Hooks, fetch.makeUrl, fetch.makeBody and fetch.fullFetchConfig receive it as data.