Get Native Function Signatures

Engine::gen_fn_signatures

As part of a reflections API, Engine::gen_fn_signatures returns a list of function signatures (as Vec<String>), each corresponding to a particular native function available to that Engine instance.

name (param 1:type 1, param 2:type 2, … , param n:type n) -> return type

The metadata feature must be used to turn on this API.

Sources

Functions from the following sources are included, in order:

  1. Native Rust functions registered into the global namespace via the Engine::register_XXX API
  2. Public (i.e. non-private) functions (native Rust or Rhai scripted) in global sub-modules registered via Engine::register_static_module.
  3. Native Rust functions in external packages registered via Engine::register_global_module
  4. Native Rust functions in built-in packages (optional)

Functions Metadata

Beware, however, that not all function signatures contain parameters and return value information.

Engine::register_XXX

For instance, functions registered via Engine::register_XXX contain no information on the names of parameter because Rust simply does not make such metadata available natively.

Type names, however, are provided.

A function registered under the name foo with three parameters.

foo(_: i64, _: char, _: &str) -> String

An operator function. Notice that function names do not need to be valid identifiers.

+=(_: &mut i64, _: i64)

A property setter. Notice that function names do not need to be valid identifiers. In this case, the first parameter should be &mut T of the custom type and the return value is ():

set$prop(_: &mut TestStruct, _: i64)

Script-Defined Functions

Script-defined function signatures contain parameter names. Since all parameters, as well as the return value, are Dynamic the types are simply not shown.

foo(x, y, z)

is probably defined simply as:

/// This is a doc-comment, included in this function's metadata.
fn foo(x, y, z) {
    ...
}

which is really the same as:

foo(x: Dynamic, y: Dynamic, z: Dynamic) -> Result<Dynamic, Box<EvalAltResult>>

Plugin Functions

Functions defined in plugin modules are the best. They contain all metadata describing the functions, including doc-comments.

For example, a plugin function combine:

/// This is a doc-comment, included in this function's metadata.
combine(list: &mut MyStruct<i64>, num: usize, name: &str) -> bool

Notice that function names do not need to be valid identifiers.

For example, an operator defined as a fallible function in a plugin module via #[rhai_fn(name="+=", return_raw)] returns Result<bool, Box<EvalAltResult>>:

+=(list: &mut MyStruct<i64>, value: &str) -> Result<bool, Box<EvalAltResult>>

For example, a property getter defined in a plugin module:

get$prop(obj: &mut MyStruct<i64>) -> String