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_archive/rhai_engine/rhaibook/rust/packages/crate.md

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+Create a Custom Package as an Independent Crate
+===============================================
+
+{{#include ../../links.md}}
+
+Creating a custom [package] as an independent crate allows it to be shared by multiple projects.
+
+```admonish abstract.small "Key concepts"
+
+* Create a Rust crate that specifies [`rhai`](https://crates.io/crates/rhai) as dependency.
+
+* The main `lib.rs` module can contain the [package] being constructed.
+```
+
+```admonish example.small
+The projects [`rhai-rand`] and [`rhai-sci`] show simple examples of creating a custom [package]
+as an independent crate.
+```
+
+
+Implementation
+--------------
+
+`Cargo.toml`:
+
+```toml
+[package]
+name = "my-package"     # 'my-package' crate
+
+[dependencies]
+rhai = "{{version}}"    # assuming {{version}} is the latest version
+```
+
+`lib.rs`:
+
+```rust
+use rhai::def_package;
+use rhai::plugin::*;
+
+// This is a plugin module
+#[export_module]
+mod my_module {
+    // Constants are ignored when used as a package
+    pub const MY_NUMBER: i64 = 42;
+
+    pub fn greet(name: &str) -> String {
+        format!("hello, {}!", name)
+    }
+    pub fn get_num() -> i64 {
+        42
+    }
+
+    // This is a sub-module, but if using combine_with_exported_module!, it will
+    // be flattened and all functions registered at the top level.
+    pub mod my_sub_module {
+        pub fn get_sub_num() -> i64 {
+            0
+        }
+    }
+}
+
+// Define the package 'MyPackage' which is exported for the crate.
+def_package! {
+    /// My own personal super package in a new crate!
+    pub MyPackage(module) {
+        combine_with_exported_module!(module, "my-functions", my_module);
+    }
+}
+```