Skip to main content

$single

$single(array, function?) -> value
Compact type signature<af?>
Browse categories
Arrays And SequencesFunctions That Use Other Functions

Source: JSONata

Documentation​

Returns exactly one item from the input sequence.

If you provide a predicate, $single() selects the items whose predicate result is truthy under JSONata boolean rules and then enforces that exactly one match exists. Without a predicate, it enforces that the input already contains exactly one item. undefined input returns undefined.

If no item matches, FUME throws D3139. If more than one item matches, FUME throws D3138. Use $first() when you want the first match without cardinality enforcement.

Examples​

Expect exactly one matching line​

Input

This example uses the claims-lines example input. The expression searches for the requested service code and asserts that exactly one line matches.

Example input

JSON
[
  {
    "claimId": "clm-2001",
    "lineNumber": 1,
    "serviceCode": "PROC-010",
    "serviceDisplay": "office visit",
    "units": 1,
    "unitPrice": 125,
    "allowedAmount": 110,
    "modifiers": [
      "MOD-A"
    ]
  },
  {
    "claimId": "clm-2001",
    "lineNumber": 2,
    "serviceCode": "PROC-020",
    "serviceDisplay": "imaging study",
    "units": "1",
    "unitPrice": 350,
    "allowedAmount": 300,
    "modifiers": [
      "MOD-B",
      "MOD-C"
    ]
  },
  {
    "claimId": "clm-2001",
    "lineNumber": 3,
    "serviceCode": "PROC-030",
    "serviceDisplay": "lab panel",
    "units": 2,
    "unitPrice": 40,
    "allowedAmount": 70,
    "modifiers": []
  },
  {
    "claimId": "clm-2002",
    "lineNumber": 1,
    "serviceCode": "PROC-010",
    "serviceDisplay": "office visit",
    "units": 1,
    "unitPrice": 125,
    "allowedAmount": 115,
    "modifiers": [
      "MOD-A"
    ]
  },
  {
    "claimId": "clm-2002",
    "lineNumber": 2,
    "serviceCode": "PROC-040",
    "serviceDisplay": "counseling",
    "units": 3,
    "unitPrice": 60,
    "allowedAmount": 150,
    "modifiers": [
      "MOD-D"
    ]
  }
]

Expression

$single($, function($l) { $l.serviceCode = "PROC-040" }).allowedAmount

Result

150