Merge pull request #2 from contextgeneric/v0.3.0

Add blog post for v0.3.0 update and new chapters

Author: soareschen

code/.gitignore

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+/target

code/Cargo.lock

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+[package]
+name = "cgp-website-examples"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "hello"
+path = "bin/hello.rs"
+
+[[bin]]
+name = "abstract-name"
+path = "bin/abstract_name.rs"
+
+[dependencies]
+cgp = { version = "0.3.0" }

code/Cargo.toml

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+use core::fmt::Display;
+
+use cgp::prelude::*; // Import all CGP constructs
+
+// Derive CGP provider traits and blanket implementations
+#[cgp_component {
+    name: GreeterComponent, // Name of the CGP component
+    provider: Greeter, // Name of the provider trait
+}]
+pub trait CanGreet // Name of the consumer trait
+{
+    fn greet(&self);
+}
+
+// Declare a CGP abstract type `Name`
+cgp_type!(Name);
+
+// A getter trait representing a dependency for `name` value
+#[cgp_auto_getter] // Derive blanket implementation
+pub trait HasName: HasNameType {
+    fn name(&self) -> &Self::Name;
+}
+
+// A provider that implements `Greeter`
+pub struct GreetHello;
+
+// Implement `Greeter` that is generic over `Context`
+impl<Context> Greeter<Context> for GreetHello
+where
+    Context: HasName, // Inject the `name` dependency from `Context`
+    Context::Name: Display,
+{
+    fn greet(context: &Context) {
+        // `self` is replaced by `context` inside providers
+        println!("Hello, {}!", context.name());
+    }
+}
+
+// A concrete context that uses CGP components
+#[derive(HasField)] // Deriving `HasField` automatically implements `HasName`
+pub struct Person {
+    pub name: String,
+}
+
+// The CGP components mapping for `Person`
+pub struct PersonComponents;
+
+// Set CGP components used by `Person` to be `PersonComponents`
+impl HasComponents for Person {
+    type Components = PersonComponents;
+}
+
+// Compile-time wiring of CGP components
+delegate_components! {
+    PersonComponents {
+        NameTypeComponent: UseType<String>,
+        GreeterComponent: GreetHello, // Use `GreetHello` to provide `Greeter`
+    }
+}
+
+fn main() {
+    let person = Person {
+        name: "Alice".into(),
+    };
+
+    // `CanGreet` is automatically implemented for `Person`
+    person.greet();
+}