values: Option<Array<JSON- Модуль
- std.
json → - Получатель
- JSON
Value - Минимальное число аргументов
- 0
- Максимальное число аргументов
- 0
Declaration and parameters
СсылкаДоступность
Включено по умолчанию · Не определено
Import std.json in language mode 5.21.
The current compiler selects std/json.tpz for this language mode. Availability in other released editions and inclusion in each installed distribution are Pending.
Получатель
JSONValue
Ограничения параметров
Bytes.length and ByteBuffer.length are read-only int properties that report the number of bytes.
JSONValue.length is an Option<int> property. Arrays and objects return Some(count) for their element or member count. Other JSON kinds return None().
JSONValue.keys and JSONValue.values are properties returning Option<Array<string>> and Option<Array<JSON. Objects return Some(keys) or Some(values). Other JSON kinds return None().
Read these properties without parentheses, as with Array.length, Map.length, Map.keys, Map.values, and Set.length. Calling a property value is rejected as a non-callable value.
Связанное правило · Read collection sizes, keys, and values as properties →JSON is an immutable JSON tree with the six JSON kinds. Reading a member preserves the tree.
as and as return Some for the matching kind and None() for every other kind. False and empty text are present values. Neither function parses text or converts a number.
number returns the exact accepted number lexeme for a number and None() for another kind. It preserves a negative zero, exponent spelling and fractional trailing zeroes.
as returns Some for a number spelled as an optional minus and decimal integer digits within the signed 64 bit range. Negative zero becomes zero. A decimal point, exponent, overflow or different kind returns None() without rounding.
as returns the elements of an array in source order. Another kind returns None(). The returned array is a separate collection. Changing that collection does not change the JSON tree.
at uses a zero based array index. A negative index, an index at or beyond the array length, or a receiver of another kind returns None(). get uses an exact decoded object key and returns None() for an absent key or another receiver kind. A present null child is Some containing JSON null.
length is a property containing the array element count or object member count. Scalar kinds yield None(). keys and values are object properties. They contain arrays in ascending Unicode scalar order of decoded keys, with corresponding positions. Array and scalar receivers yield None() for both properties.
The receiver and supplied arguments are evaluated once in ordinary call order. Inspection performs no I/O and invokes no user conversion. Incorrect argument types follow ordinary checking diagnostics rather than becoming absent values.
Связанное правило · Project JSON values without coercion →Результат
The declared result type is Option<Array<JSON.
Эффекты
Ошибки
Result and effects
СсылкаSelect this field from a value of its named type without call parentheses.
Read object children in the same order as the keys property.
Why
СсылкаCollection observations use the same property syntax as Array, Map, and Set. Parentheses identify calls rather than stored or derived values.
Related entries
СсылкаRead collection sizes, keys, and values as properties
СсылкаRead collection sizes, keys, and values as properties
Bytes.length and ByteBuffer.length are read-only int properties that report the number of bytes.
JSONValue.length is an Option<int> property. Arrays and objects return Some(count) for their element or member count. Other JSON kinds return None().
JSONValue.keys and JSONValue.values are properties returning Option<Array<string>> and Option<Array<JSON. Objects return Some(keys) or Some(values). Other JSON kinds return None().
Read these properties without parentheses, as with Array.length, Map.length, Map.keys, Map.values, and Set.length. Calling a property value is rejected as a non-callable value.
Причина
The same collection observation should use the same syntax across core collections and library values. Keeping JSONValue results optional preserves its distinction between collections and scalar values.
Read the same properties on core collections
Ссылкаimport std.iolet array = [2, 3]let entries = map { "name": "Topaz" }let values = set { 2, 3 }io.writeLine("{array.length}:{entries.length}:{values.length}")io.writeLine(entries.keys[0])io.writeLine(entries.values[0])
2:1:2
name
Topaz
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
2:1:2nameTopaz
Read a byte sequence size
Ссылкаimport std.bytes { Bytes }import std.iolet bytes = Bytes.empty()let size: int = bytes.lengthio.writeLine("{size}")
0
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
0
Read a byte buffer size
Ссылкаimport std.bytes { ByteBuffer }import std.iolet buffer = ByteBuffer.allocate(3)let size: int = buffer.lengthio.writeLine("{size}")
3
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
3
Read JSON sizes and preserve optional results
Ссылкаimport std.jsonimport std.testimport std.iolet array = test.assertOk(json.parse("[1,2]"))let object = test.assertOk(json.parse("\{\"name\":\"Topaz\"\}"))let scalar = test.assertOk(json.parse("42"))let arraySize: Option<int> = array.lengthlet objectSize: Option<int> = object.lengthlet scalarSize: Option<int> = scalar.lengthtest.assertEq(test.assertSome(arraySize), 2)test.assertEq(test.assertSome(objectSize), 1)test.assertNone(scalarSize)io.writeLine("JSON sizes read")
JSON sizes read
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
JSON sizes read
Read JSON object keys
Ссылкаimport std.jsonimport std.testimport std.iolet object = test.assertOk(json.parse("\{\"name\":\"Topaz\"\}"))let array = test.assertOk(json.parse("[]"))let scalar = test.assertOk(json.parse("42"))let names: Option<Array<string>> = object.keystest.assertEq(test.assertSome(names)[0], "name")test.assertNone(array.keys)test.assertNone(scalar.keys)io.writeLine("JSON keys read")
JSON keys read
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
JSON keys read
Read JSON object values
Ссылкаimport std.jsonimport std.testimport std.iolet object = test.assertOk(json.parse("\{\"name\":\"Topaz\"\}"))let array = test.assertOk(json.parse("[]"))let scalar = test.assertOk(json.parse("42"))let values = test.assertSome(object.values)test.assertEq(test.assertSome(values[0].asString()), "Topaz")test.assertNone(array.values)test.assertNone(scalar.values)io.writeLine("JSON values read")
JSON values read
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
JSON values read
Reject calling Bytes.length
Ссылкаimport std.bytes { Bytes }function inspect(value: Bytes) -> () {let result = value.length()return ()}
Нет стандартного вывода.Ожидаемый результат
Ожидаемый результат
Этап отклонения check. Ненулевой код завершения.
stdlib-property-not-callable at
main.tpz:3:22
Reject calling ByteBuffer.length
Ссылкаimport std.bytes { ByteBuffer }function inspect(value: ByteBuffer) -> () {let result = value.length()return ()}
Нет стандартного вывода.Ожидаемый результат
Ожидаемый результат
Этап отклонения check. Ненулевой код завершения.
stdlib-property-not-callable at
main.tpz:3:22
Reject calling JSONValue.length
Ссылкаimport std.json { JSONValue }function inspect(value: JSONValue) -> () {let result = value.length()return ()}
Нет стандартного вывода.Ожидаемый результат
Ожидаемый результат
Этап отклонения check. Ненулевой код завершения.
stdlib-property-not-callable at
main.tpz:3:22
Reject calling JSONValue.keys
Ссылкаimport std.json { JSONValue }function inspect(value: JSONValue) -> () {let result = value.keys()return ()}
Нет стандартного вывода.Ожидаемый результат
Ожидаемый результат
Этап отклонения check. Ненулевой код завершения.
stdlib-property-not-callable at
main.tpz:3:22
Reject calling JSONValue.values
Ссылкаimport std.json { JSONValue }function inspect(value: JSONValue) -> () {let result = value.values()return ()}
Нет стандартного вывода.Ожидаемый результат
Ожидаемый результат
Этап отклонения check. Ненулевой код завершения.
stdlib-property-not-callable at
main.tpz:3:22
Diagnostics
СсылкаProject JSON values without coercion
СсылкаProject JSON values without coercion
JSON is an immutable JSON tree with the six JSON kinds. Reading a member preserves the tree.
as and as return Some for the matching kind and None() for every other kind. False and empty text are present values. Neither function parses text or converts a number.
number returns the exact accepted number lexeme for a number and None() for another kind. It preserves a negative zero, exponent spelling and fractional trailing zeroes.
as returns Some for a number spelled as an optional minus and decimal integer digits within the signed 64 bit range. Negative zero becomes zero. A decimal point, exponent, overflow or different kind returns None() without rounding.
as returns the elements of an array in source order. Another kind returns None(). The returned array is a separate collection. Changing that collection does not change the JSON tree.
at uses a zero based array index. A negative index, an index at or beyond the array length, or a receiver of another kind returns None(). get uses an exact decoded object key and returns None() for an absent key or another receiver kind. A present null child is Some containing JSON null.
length is a property containing the array element count or object member count. Scalar kinds yield None(). keys and values are object properties. They contain arrays in ascending Unicode scalar order of decoded keys, with corresponding positions. Array and scalar receivers yield None() for both properties.
The receiver and supplied arguments are evaluated once in ordinary call order. Inspection performs no I/O and invokes no user conversion. Incorrect argument types follow ordinary checking diagnostics rather than becoming absent values.
Причина
Optional projection keeps a missing child distinct from a stored null. Number text preserves the original representation, while the integer projection has an explicit spelling and range. Sorted key and value positions support deterministic traversal.
Inspect present values and missing children
Ссылкаimport std.jsonimport std.testimport std.iolet value = test.assertOk(json.parse("[false,\"\",null,7]"))let items = test.assertSome(value.asArray())test.assertEq(test.assertSome(items[0].asBool()), false)test.assertEq(test.assertSome(items[1].asString()), "")test.assertEq(items[2].kind(), "null")test.assertEq(test.assertSome(items[3].asInt()), 7)test.assertNone(value.at(-1))test.assertNone(value.at(4))test.assertNone(value.get("0"))test.assertNone(items[0].asString())test.assertNone(items[1].numberText())test.assertNone(items[2].asArray())let object = test.assertOk(json.parse("\{\"present\":null\}"))test.assertEq(test.assertSome(object.get("present")).kind(), "null")test.assertNone(object.get("missing"))test.assertNone(object.at(0))io.writeLine("present values remain distinct from missing children")
present values remain distinct from missing children
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
present values remain distinct from missing children
Keep integer projection within the declared spelling and range
Ссылкаimport std.jsonimport std.testimport std.iofor text in (["-9223372036854775808", "9223372036854775807", "9223372036854775808", "-0", "1.0", "1e0", "1.5"]) {let value = test.assertOk(json.parse(text))match (value.asInt()) {case Some(number) => io.writeLine("{text} = {number}")case None() => io.writeLine("{text} = none")}}
-9223372036854775808 = -9223372036854775808
9223372036854775807 = 9223372036854775807
9223372036854775808 = none
-0 = 0
1.0 = none
1e0 = none
1.5 = none
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
-9223372036854775808 = -92233720368547758089223372036854775807 = 92233720368547758079223372036854775808 = none-0 = 01.0 = none1e0 = none1.5 = none
Read matching keys and values in scalar order
Ссылкаimport std.jsonimport std.testimport std.iolet object = test.assertOk(json.parse("\{\"z\":1,\"a\":null\}"))let names = test.assertSome(object.keys)let values = test.assertSome(object.values)test.assertEq(test.assertSome(object.length), 2)io.writeLine("{names[0]} = {values[0].kind()}")io.writeLine("{names[1]} = {test.assertSome(values[1].asInt())}")let array = test.assertOk(json.parse("[]"))test.assertEq(test.assertSome(array.length), 0)test.assertNone(array.keys)test.assertNone(array.values)let scalar = test.assertOk(json.parse("\"text\""))test.assertNone(scalar.length)
a = null
z = 1
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
a = nullz = 1