rhaj/_archive/rhai_engine/rhaibook/language/dynamic.md

Dynamic Values

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A Dynamic value can be any type, as long as it implements Clone.

Under the [`sync`] feature, all types must also be `Send + Sync`.

let x = 42;         // value is an integer

x = 123.456;        // value is now a floating-point number

x = "hello";        // value is now a string

x = x.len > 0;      // value is now a boolean

x = [x];            // value is now an array

x = #{x: x};        // value is now an object map

Use type_of() to Get Value Type

Because [type_of()] a Dynamic value returns the type of the actual value, it is usually used to perform type-specific actions based on the actual value's type.

let mystery = get_some_dynamic_value();

switch type_of(mystery) {
    "()" => print("Hey, I got the unit () here!"),
    "i64" => print("Hey, I got an integer here!"),
    "f64" => print("Hey, I got a float here!"),
    "decimal" => print("Hey, I got a decimal here!"),
    "range" => print("Hey, I got an exclusive range here!"),
    "range=" => print("Hey, I got an inclusive range here!"),
    "string" => print("Hey, I got a string here!"),
    "bool" => print("Hey, I got a boolean here!"),
    "array" => print("Hey, I got an array here!"),
    "blob" => print("Hey, I got a BLOB here!"),
    "map" => print("Hey, I got an object map here!"),
    "Fn" => print("Hey, I got a function pointer here!"),
    "timestamp" => print("Hey, I got a time-stamp here!"),
    "TestStruct" => print("Hey, I got the TestStruct custom type here!"),
    _ => print(`I don't know what this is: ${type_of(mystery)}`)
}

Parse from JSON

`parse_json` is defined in the [`LanguageCorePackage`][built-in packages], which is excluded when using a [raw `Engine`].

It also requires the [`metadata`] feature; the [`no_index`] and [`no_object`] features must _not_ be set.

Use parse_json to parse a JSON string into a [Dynamic] value.

JSON type	Rhai type
number (no decimal point)	INT
number (with decimal point)	FLOAT
string	[string]
boolean	bool
Array	[array]
Object	[object map]
null	[()]