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Библиотека · std.json

JSONValue.asInt

Attempts to read this JSON value as an int.

asInt() -> Option<int>

Модуль: std.json →
Получатель: JSONValue
Минимальное число аргументов: 0
Максимальное число аргументов: 0

Declaration and parameters

Доступность

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

Дополнительные контракты не определены.

JSONValue is an immutable JSON tree with the six JSON kinds. Reading a member preserves the tree.

asBool and asString 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.

numberText 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.

asInt 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.

asArray 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

Дополнительные контракты не определены.

The declared result type is Option<int>.

Эффекты

Не определено

Ошибки

Не определено

Result and effects

Project a signed decimal integer lexeme within the int range without rounding.

Project JSON values without coercion

Правилоtopaz.stdlib.contract.json-value.rule

Project JSON values without coercion

JSONValue is an immutable JSON tree with the six JSON kinds. Reading a member preserves the tree.

asBool and asString 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.

numberText 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.

asInt 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.

asArray 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.

Примеры Inspect present values and missing children →Keep integer projection within the declared spelling and range →Read matching keys and values in scalar order →

Inspect present values and missing children

run · running · Проверка · Не выполнялось

main.tpzInspect present values and missing childrenОткрыть песочницу →

import std.json
import std.test
import std.io
let 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")

Ожидаемый выводКод завершения 0

present values remain distinct from missing children

$ topaz run main.tpz · Целевой продукт 5.21.3

Ожидаемый результат

Ожидаемый результат

Выполнение завершается. Код завершения 0.

Нет вывода ошибок.

Ожидаемый стандартный вывод

present values remain distinct from missing children

Этот пример ещё не выполнялся.

Keep integer projection within the declared spelling and range

run · running · Проверка · Не выполнялось

main.tpzKeep integer projection within the declared spelling and rangeОткрыть песочницу →

import std.json
import std.test
import std.io
for 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")
}
}

Ожидаемый выводКод завершения 0

-9223372036854775808 = -9223372036854775808
9223372036854775807 = 9223372036854775807
9223372036854775808 = none
-0 = 0
1.0 = none
1e0 = none
1.5 = none

$ topaz run main.tpz · Целевой продукт 5.21.3

Ожидаемый результат

Ожидаемый результат

Выполнение завершается. Код завершения 0.

Нет вывода ошибок.

Ожидаемый стандартный вывод

-9223372036854775808 = -9223372036854775808
9223372036854775807 = 9223372036854775807
9223372036854775808 = none
-0 = 0
1.0 = none
1e0 = none
1.5 = none

Этот пример ещё не выполнялся.

Read matching keys and values in scalar order

run · running · Проверка · Не выполнялось

main.tpzRead matching keys and values in scalar orderОткрыть песочницу →

import std.json
import std.test
import std.io
let 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)

Ожидаемый выводКод завершения 0

a = null
z = 1

$ topaz run main.tpz · Целевой продукт 5.21.3

Ожидаемый результат

Ожидаемый результат

Выполнение завершается. Код завершения 0.

Нет вывода ошибок.

Ожидаемый стандартный вывод

a = null
z = 1

Этот пример ещё не выполнялся.