Learning CoB

# $ref() - Fields Referencing Other Fields

Fields built with this keyword are used when, in an instance, we intend to make a reference to one - and only one - Instance of the same or another definition. By linking an instance to another instance, we can access the information properties of the linked instance. Although an instance can only point to one instance, several instances can reference the same instance. While fields of type $ref() normally point to instances of other definitions, there can be scenarios where it is advantageous to create a tree of instances within the same definition. In this case, we can mark the field as $ref of that definition.

# Usage:

$ref(definition_name, query)

The first argument must be the name of the definition where we want to search and the second the particular instance of that definition from which we want to show related results.

Options:

  • definition_name - The name of the definition to pull the data
  • query: The query to use to get data from the definition

To see how to search for references to instances of other definitions in fields built with the $ref() keyword, read this article.

WARNING

When we have a definition with a field of type $ref() that references a definition whose $instanceLabel field is also a field of type $ref(), we will obtain in the listing of the initial definition the value of the $ref() field of the intermediate definition, i.e. the id of the referenced instance of the third definition. To actually get the value of the $instanceLabel field of the third definition, the $instanceLabel field of the second definition will have to be a $auto.ref(),field() for the field of the third definition that we want to show in the listing of the first definition.

# Examples:

In the following example we are using the expression $ref(Countries,*) in order to allow a user to search for field values within all instances of the Countries definition.

To identify fields of type $ref() you have to look for any field that has on its right side a magnifying glass. These fields allow you to search for instances of another definition.

Check the video included below if you want to know how to build definition fields with the $ref() keyword:

← $extRef() - External Reference Fields →