Using types defined outside a UDL.

Often you need to refer to types described outside of this UDL - they may be defined in a proc-macro in this crate or defined in an external crate.

You declare such types using:

typedef [type] [TypeName];

TypeName is then able to be used as a normal type in this UDL (ie, be returned from functions, in records, etc)

type indicates the actual type of TypeName and can be any of the following values: * "enum" for Enums. * "record", "dictionary" or "struct" for Records. * "object", "impl" or "interface" for objects. * "trait", "callback" or "trait_with_foreign" for traits. * "custom" for Custom Types.

for example, if this crate has:

#[derive(::uniffi::Object)]
struct MyObject { ... }

our UDL could use this type with:

typedef interface MyObject;

External Crates

The [External="crate_name"] attribute can be used whenever the type is in another crate - whether in UDL or in a proc-macro.

[External = "other_crate"]
typedef interface OtherObject;