IsNull

IsNull( value )
IsNull( value )
IsNull( value )
IsNull( value )
Not available in this language yet.
Not available in this language yet.

Description

The IsNull function returns true only if value is a null, otherwise it returns false.

Parameters

Argument Type Definition and Requirements

value

Any

Any value, which is to be tested to determine whether it is a null or not.

Returns

Returns a boolean, indicating whether value was a null or not.

Examples

The following query uses Map to iterate over an array of all of the types of values that can be tested by a type-check function, passing each item into a Lambda function that returns an object, which contains the value and the result of calling IsNull with that value:

result, err := client.Query(
  f.Map(
    f.Arr{
      f.Arr{"array"},
      true,
      false,
      f.BytesV{0x01, 0x02, 0x03, 0x04},
      f.Arr{0x1, 0x2, 0x3, 0x4},
      f.Collection("Letters"),
      f.Ref("credentials/self"),
      f.Database("child_db"),
      f.Date("2019-11-12"),
      f.RefCollection(f.Collection("Letters"), 123),
      10.1,
      f.Function("double"),
      f.Index("all_letters"),
      10,
      f.RefCollection(f.Keys(), "248967241620521472"),
      f.Query(f.Lambda("x", f.Var("x"))),
      nil,
      f.Null(),
      f.Obj{ "x": 10 },
      f.Role("employees"),
      f.Match(f.Index("all_letters")),
      "ten",
      "10",
      f.Now(),
      f.RefCollection(f.Tokens(), "249062079147803136"),
    },
    f.Lambda("x", f.Obj{
      "value": f.Var("x"),
      "IsNull": f.IsNull(f.Var("x")),
    })))

if (err != nil) {
  fmt.Println(err)
} else {
  fmt.Println(result)
}
System.out.println(
    client.query(
        Map(
            Arr(
                Arr(Value("array")),
                Value(true),
                Value(false),
                Value(new byte[] {0x1, 0x2, 0x3, 0x4}),
                Arr(Value(0x1), Value(0x2), Value(0x3), Value(0x4)),
                Collection("Letters"),
                Ref("credentials/self"),
                Database("child_db"),
                Date("2019-11-12"),
                Ref(Collection("Letters"), "123"),
                Value(10.1),
                Function("double"),
                Index("all_letters"),
                Value(10),
                Ref(Keys(), "248967241620521472"),
                Query(Lambda("x", Var("x"))),
                Null(),
                Obj("x", Value(10)),
                Role("employees"),
                Match(Index("all_letters")),
                Value("ten"),
                Value("10"),
                Now(),
                Ref(Tokens(), "249062079147803136")
            ),
            Lambda(
                "x",
                Obj("value", Var("x"), "IsNull", IsNull(Var("x")))
            )
        )
    ).get());
client.query(
  q.Map(
    [
      ['array'],
      true,
      false,
      new Uint8Array([1, 2, 3, 4]),
      [0x1, 0x2, 0x3, 0x4],
      q.Collection('Letters'),
      q.Ref('credentials/self'),
      q.Database('child_db'),
      q.Date('2019-11-12'),
      q.Ref(q.Collection('Letters'), 123),
      10.1,
      q.Function('double'),
      q.Index('all_letters'),
      10,
      q.Ref(q.Keys(), '248967241620521472'),
      q.Query(q.Lambda('x', q.Var('x'))),
      null,
      { x: 10 },
      q.Role('employees'),
      q.Match(q.Index('all_letters')),
      'ten',
      '10',
      q.Now(),
      q.Ref(q.Tokens(), '249062079147803136'),
    ],
    q.Lambda('x', {
      value: q.Var('x'),
      IsNull: q.IsNull(q.Var('x')),
    })
  )
)
.then((ret) => console.log(ret))
println(Await.result(
  client.query(
    Map(
      Arr(
        Arr("array"),
        true,
        false,
        BytesV(0x1, 0x2, 0x3, 0x4),
        Arr(0x1, 0x2, 0x3, 0x4),
        Collection("Letters"),
        Ref("credentials/self"),
        Database("child_db"),
        Date("2019-11-12"),
        Ref(Collection("Letters"), 123),
        10.1,
        Function("double"),
        Index("all_letters"),
        10,
        Ref(Keys(), "248967241620521472"),
        Query(Lambda("x", Var("x"))),
        Null,
        Obj("x" -> 10),
        Role("employees"),
        Match(Index("all_letters")),
        "ten",
        "10",
        Now(),
        Ref(Tokens(), "249062079147803136")
      ),
      Lambda(
        "x",
        Obj( "value" -> Var("x"), "IsNull" -> IsNull(Var("x")))
      )
    )
  ),
  5.seconds
))
Not available in this language yet.
Not available in this language yet.
[map[IsNull:false value:[array]] map[IsNull:false value:true] map[IsNull:false value:false] map[IsNull:false value:[1 2 3 4]] map[IsNull:false value:[1 2 3 4]] map[IsNull:false value:{Letters 0xc00008f8f0 0xc00008f8f0 <nil>}] map[IsNull:false value:{264354436692836874 0xc00008fa10 0xc00008fa10 <nil>}] map[IsNull:false value:{child_db 0xc00008fb30 0xc00008fb30 <nil>}] map[IsNull:false value:{0 63709113600 <nil>}] map[IsNull:false value:{123 0xc00008fd40 0xc00008fd40 <nil>}] map[IsNull:false value:10.1] map[IsNull:false value:{double 0xc00008fe90 0xc00008fe90 <nil>}] map[IsNull:false value:{all_letters 0xc00008ffb0 0xc00008ffb0 <nil>}] map[IsNull:false value:10] map[IsNull:false value:{248967241620521472 0xc0004a4300 0xc0004a4300 <nil>}] map[IsNull:false value:{[123 34 108 97 109 98 100 97 34 58 34 120 34 44 34 101 120 112 114 34 58 123 34 118 97 114 34 58 34 120 34 125 125]}] map[IsNull:true value:{}] map[IsNull:true value:{}] map[IsNull:false value:map[x:10]] map[IsNull:false value:{employees 0xc0004a4510 0xc0004a4510 <nil>}] map[IsNull:false value:{map[match:{all_letters 0xc0004a4660 0xc0004a4660 <nil>}]}] map[IsNull:false value:ten] map[IsNull:false value:10] map[IsNull:false value:{620860000 63724302491 <nil>}] map[IsNull:false value:{249062079147803136 0xc0004a4810 0xc0004a4810 <nil>}]]
[{value: ["array"], IsNull: false},
 {value: true, IsNull: false},
 {value: false, IsNull: false},
 {value: [0x01 0x02 0x03 0x04], IsNull: false},
 {value: [1, 2, 3, 4], IsNull: false},
 {value: ref(id = "Letters", collection = ref(id = "collections")),
  IsNull: false},
 {value: ref(id = "248967019900174848", collection = ref(id = "credentials")),
  IsNull: false},
 {value: ref(id = "child_db", collection = ref(id = "databases")),
  IsNull: false},
 {value: 2019-11-12, IsNull: false},
 {value: ref(id = "123", collection = ref(id = "Letters", collection = ref(id = "collections"))),
  IsNull: false},
 {value: 10.1, IsNull: false},
 {value: ref(id = "double", collection = ref(id = "functions")),
  IsNull: false},
 {value: ref(id = "all_letters", collection = ref(id = "indexes")),
  IsNull: false},
 {value: 10, IsNull: false},
 {value: ref(id = "248967241620521472", collection = ref(id = "keys")),
  IsNull: false},
 {value: QueryV({lambda=x, expr={var=x}}), IsNull: false},
 {value: null, IsNull: true},
 {value: {x: 10}, IsNull: false},
 {value: ref(id = "employees", collection = ref(id = "roles")),
  IsNull: false},
 {value: {@set = {match: ref(id = "all_letters", collection = ref(id = "indexes"))}},
  IsNull: false},
 {value: "ten", IsNull: false},
 {value: "10", IsNull: false},
 {value: 2019-11-12T13:15:16.789Z, IsNull: false},
 {value: ref(id = "249062079147803136", collection = ref(id = "tokens")),
  IsNull: false}]
[ { value: [ 'array' ], IsNull: false },
  { value: true, IsNull: false },
  { value: false, IsNull: false },
  { value: Bytes("AQIDBA=="), IsNull: false },
  { value: [ 1, 2, 3, 4 ], IsNull: false },
  { value: Collection("Letters"), IsNull: false },
  { value: Ref(Credentials(), "248967019900174848"),
    IsNull: false },
  { value: Database("child_db"), IsNull: false },
  { value: Date("2019-11-12"), IsNull: false },
  { value: Ref(Collection("Letters"), "123"), IsNull: false },
  { value: 10.1, IsNull: false },
  { value: Function("double"), IsNull: false },
  { value: Index("all_letters"), IsNull: false },
  { value: 10, IsNull: false },
  { value: Ref(Keys(), "248967241620521472"), IsNull: false },
  { value: Query(Lambda("x", Var("x"))), IsNull: false },
  { value: null, IsNull: true },
  { value: { x: 10 }, IsNull: false },
  { value: Role("employees"), IsNull: false },
  { value: Match(Index("all_letters")), IsNull: false },
  { value: 'ten', IsNull: false },
  { value: '10', IsNull: false },
  { value: Time("2019-11-12T13:15:16.789Z"), IsNull: false },
  { value: Ref(Tokens(), "249062079147803136"), IsNull: false } ]
[{value: ["array"], IsNull: false},
 {value: true, IsNull: false},
 {value: false, IsNull: false},
 {value: [0x01 0x02 0x03 0x04], IsNull: false},
 {value: [1, 2, 3, 4], IsNull: false},
 {value: ref(id = "Letters", collection = ref(id = "collections")),
  IsNull: false},
 {value: ref(id = "248967019900174848", collection = ref(id = "credentials")),
  IsNull: false},
 {value: ref(id = "child_db", collection = ref(id = "databases")),
  IsNull: false},
 {value: 2019-11-12, IsNull: false},
 {value: ref(id = "123", collection = ref(id = "Letters", collection = ref(id = "collections"))),
  IsNull: false},
 {value: 10.1, IsNull: false},
 {value: ref(id = "double", collection = ref(id = "functions")),
  IsNull: false},
 {value: ref(id = "all_letters", collection = ref(id = "indexes")),
  IsNull: false},
 {value: 10, IsNull: false},
 {value: ref(id = "248967241620521472", collection = ref(id = "keys")),
  IsNull: false},
 {value: {lambda: "x", expr: {var: "x"}}, IsNull: false},
 {value: NullV, IsNull: true},
 {value: {x: 10}, IsNull: false},
 {value: ref(id = "employees", collection = ref(id = "roles")),
  IsNull: false},
 {value: {@set = {match: ref(id = "all_letters", collection = ref(id = "indexes"))}},
  IsNull: false},
 {value: "ten", IsNull: false},
 {value: "10", IsNull: false},
 {value: 2019-11-12T13:15:16.789Z, IsNull: false},
 {value: ref(id = "249062079147803136", collection = ref(id = "tokens")),
  IsNull: false}]

This query operates on a pre-existing schema, which is not provided here.

Also, the query is executed via a client connection, that uses a secret acquired by calling Login (not shown here), so that Ref("credentials/self") returns a valid value.

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