Json Value¶

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import "std/text/json-value";

JsonValue struct¶

Represents a single JSON value.

Composite values (arrays and objects) own their children as heap pointers, so a JsonValue is always reached via heap JsonValue* once it has been parsed. Numbers are stored as double; integers are representable up to 2^53. Object fields preserve insertion order.

Destroying a value recursively destroys everything below it, so a whole tree is released with a single deleteJsonValue call on its root. Accessors like getField hand out borrowed pointers that stay owned by their parent, while addArrayItem and addObjectField take ownership of what they are given.

Note that the root cannot simply be held in a heap JsonValue* and left to the compiler: the heap qualifier only emits a raw deallocation when the variable goes out of scope and never runs the destructor of the pointee, so the children below the root would be lost.

Parsing lives in "std/text/json/json-parser" and serialization in "std/text/json/json-serializer", so programs only pull in what they use.

Constructors¶

ctor¶

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public p JsonValue.ctor()

Construct a JSON null value

ctor¶

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public p JsonValue.ctor(JsonValueKind kind)

Construct an empty JSON value of the given kind. Useful for building arrays and objects from scratch.

Parameters

ctor¶

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public p JsonValue.ctor(bool value)

Construct a JSON boolean value

Parameters

ctor¶

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public p JsonValue.ctor(double value)

Construct a JSON number value

Parameters

ctor¶

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public p JsonValue.ctor(const String& value)

Construct a JSON string value

Parameters

dtor¶

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public p JsonValue.dtor()

Destruct the JSON value, releasing every array item and object field it owns. Since the children are destroyed the same way, this tears down the whole subtree below the value.

Methods¶

getKind¶

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public f<JsonValueKind> JsonValue.getKind()

Retrieve the kind of the JSON value

Returns: JsonValueKind — Kind of the value

isNull¶

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public f<bool> JsonValue.isNull()

Check whether the JSON value is null

Returns: bool — true if the value is null, false otherwise

isBool¶

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public f<bool> JsonValue.isBool()

Check whether the JSON value is a boolean

Returns: bool — true if the value is a boolean, false otherwise

isNumber¶

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public f<bool> JsonValue.isNumber()

Check whether the JSON value is a number

Returns: bool — true if the value is a number, false otherwise

isString¶

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public f<bool> JsonValue.isString()

Check whether the JSON value is a string

Returns: bool — true if the value is a string, false otherwise

isArray¶

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public f<bool> JsonValue.isArray()

Check whether the JSON value is an array

Returns: bool — true if the value is an array, false otherwise

isObject¶

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public f<bool> JsonValue.isObject()

Check whether the JSON value is an object

Returns: bool — true if the value is an object, false otherwise

getBool¶

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public f<bool> JsonValue.getBool()

Retrieve the boolean payload. Panics if the value is not a boolean.

Returns: bool — Boolean value

getNumber¶

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public f<double> JsonValue.getNumber()

Retrieve the number payload. Panics if the value is not a number.

Returns: double — Number value

getString¶

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public f<const String&> JsonValue.getString()

Retrieve the string payload. Panics if the value is not a string.

Returns: const String& — String value

getArraySize¶

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public f<unsigned long> JsonValue.getArraySize()

Retrieve the number of items in the array. Panics if the value is not an array.

Returns: unsigned long — Number of array items

getArrayItem¶

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public f<JsonValue*> JsonValue.getArrayItem(unsigned long idx)

Retrieve the array item at the given index. Panics if the value is not an array.

Parameters

Returns: JsonValue* — Pointer to the array item

getArrayItem¶

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public f<JsonValue*> JsonValue.getArrayItem(unsigned int idx)

Retrieve the array item at the given index. Panics if the value is not an array.

Parameters

Returns: JsonValue* — Pointer to the array item

addArrayItem¶

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public p JsonValue.addArrayItem(JsonValue* item)

Append an item to the array. Panics if the value is not an array. The array takes ownership of the heap-allocated item.

Parameters

getObjectSize¶

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public f<unsigned long> JsonValue.getObjectSize()

Retrieve the number of fields in the object. Panics if the value is not an object.

Returns: unsigned long — Number of object fields

getObjectKey¶

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public f<const String&> JsonValue.getObjectKey(unsigned long idx)

Retrieve the key of the object field at the given index, in insertion order. Panics if the value is not an object.

Parameters

Returns: const String& — Field key

getObjectValue¶

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public f<JsonValue*> JsonValue.getObjectValue(unsigned long idx)

Retrieve the value of the object field at the given index, in insertion order. Panics if the value is not an object.

Parameters

Returns: JsonValue* — Pointer to the field value

hasField¶

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public f<bool> JsonValue.hasField(string key)

Check whether the object contains a field with the given key

Parameters

Returns: bool — true if the field exists, false otherwise

getField¶

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public f<JsonValue*> JsonValue.getField(string key)

Retrieve the value of the object field with the given key. Panics if the value is not an object or the field does not exist.

Parameters

Returns: JsonValue* — Pointer to the field value

addObjectField¶

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public p JsonValue.addObjectField(const String& key, JsonValue* value)

Append a field to the object. Panics if the value is not an object. The object takes ownership of the heap-allocated field value.

Parameters

Functions¶

deleteJsonValue¶

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public p deleteJsonValue(JsonValue*& value)

Destroys a heap-allocated JSON value together with everything it owns and sets the given handle to nil, so releasing a whole tree only takes one call on its root.

Note that this is what sDelete would normally be used for. It cannot be used here, because a value tree is destroyed recursively and the compiler does not emit an explicit dtor that is only reached through sDestruct.

Parameters

JsonValueKind enum¶

Tag for the variant stored inside a JsonValue.