Add LazyRes for lazy resource initialization

1 files changed, 92 insertions, 0 deletions

diff --git a/examples/example-lazy-resources/src/main.rs b/examples/example-lazy-resources/src/main.rs
new file mode 100644
index 0000000..3533ae2
--- /dev/null
+++ b/examples/example-lazy-resources/src/main.rs
@@ -0,0 +1,92 @@
+//! Example Lazy Resources
+//!
+//! > This example demonstrates how to use `LazyRes` for lazy resource initialization.
+//!
+//! Run:
+//! ```bash
+//! cargo run --manifest-path examples/example-lazy-resources/Cargo.toml --quiet none
+//!
+//! cargo run --manifest-path examples/example-lazy-resources/Cargo.toml --quiet show
+//! ```
+//!
+//! Output:
+//! ```plaintext
+//! None
+//!
+//! Initialized
+//! foo: bar
+//! rust: lang
+//! baz: qux
+//! hello: world
+//! key: value
+//! ```
+
+use std::collections::BTreeMap;
+
+use mingling::{LazyInit, LazyRes, prelude::*};
+
+type Key = String;
+type Value = String;
+
+// Define a resource that requires time-consuming initialization
+#[derive(Default, Clone)]
+pub struct ResLargeData {
+    pub data: BTreeMap<Key, Value>,
+}
+
+fn init_res_large_data() -> ResLargeData {
+    // Perform time-consuming initialization here
+    let mut data = BTreeMap::new();
+    data.insert("foo".to_string(), "bar".to_string());
+    data.insert("baz".to_string(), "qux".to_string());
+    data.insert("hello".to_string(), "world".to_string());
+    data.insert("rust".to_string(), "lang".to_string());
+    data.insert("key".to_string(), "value".to_string());
+
+    // Print to indicate initialization is complete
+    println!("Initialized");
+    ResLargeData { data }
+}
+
+dispatcher!("show", CMDShow => EntryShow);
+dispatcher!("none", CMDNone => EntryNone);
+
+pack!(ResultShow = BTreeMap<Key, Value>);
+
+fn main() {
+    let mut program = ThisProgram::new();
+
+    // --------- IMPORTANT ---------
+    //                     _ Use lazy_init to create LazyRes<ResLargeData>
+    //                    /
+    //                    vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+    program.with_resource(ResLargeData::lazy_init(init_res_large_data));
+    // --------- IMPORTANT ---------
+
+    program.with_dispatchers((CMDShow, CMDNone));
+    program.exec_and_exit();
+}
+
+// Inject LazyRes instead of a normal resource
+//                                           __________________________ Must use &mut because `get_ref` and `get_mut`
+//                                          /                             both require mutable borrow
+//                                          |     _____________________ Use LazyRes<ResLargeData>
+//                                          |    /                        instead of ResLargeData
+#[renderer] //                              vvvv vvvvvvvvvvvvvvvvvvvvv
+fn render_entry_show(_args: EntryShow, res: &mut LazyRes<ResLargeData>) {
+    //             _______ Initialization happens here
+    //            /
+    //            vvvvvvv
+    let res = res.get_ref();
+    for (key, value) in &res.data {
+        r_println!("{}: {}", key, value);
+    }
+}
+
+// When not using LazyRes<ResLargeData>, it will not be initialized
+#[renderer]
+fn render_entry_none(_args: EntryNone) {
+    r_println!("None");
+}
+
+gen_program!();