Iterator pattern: starnard and custom

Author: fadeevab

Cargo.toml

@@ -18,4 +18,5 @@ members = [
   "structural/proxy",
   "behavioral/chain-of-responsibility",
   "behavioral/command",
+  "behavioral/iterator",
 ]

behavioral/iterator/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+edition = "2021"
+name = "iterator"
+version = "0.1.0"
+
+[[bin]]
+name = "iterator"
+path = "main.rs"

behavioral/iterator/README.md

@@ -0,0 +1,38 @@
+# Iterator
+
+Iterator is a behavioral design pattern that allows sequential traversal through a complex data structure without exposing its internal details.
+
+## Standard Iterator
+
+```rust
+let array = &[1, 2, 3];
+let iterator = array.iter();
+
+// Traversal over each element of the vector.
+iterator.for_each(|e| print!("{}, ", e));
+```
+
+## Custom Iterator
+
+```rust
+let users = UserCollection::new();
+let mut iterator = users.iter();
+
+iterator.next();
+```
+
+## Execution Result
+
+```
+Iterators are widely used in the standard library: 1 2 3
+
+Let's test our own iterator.
+
+1nd element: Some("Alice")
+2nd element: Some("Bob")
+3rd element: Some("Carl")
+4th element: None
+
+
+All elements in user collection: Alice Bob Carl
+```

behavioral/iterator/main.rs

@@ -0,0 +1,28 @@
+use crate::users::UserCollection;
+
+mod users;
+
+fn main() {
+    print!("Iterators are widely used in the standard library: ");
+
+    let array = &[1, 2, 3];
+    let iterator = array.iter();
+
+    // Traversal over each element of the array.
+    iterator.for_each(|e| print!("{} ", e));
+
+    println!("\n\nLet's test our own iterator.\n");
+
+    let users = UserCollection::new();
+    let mut iterator = users.iter();
+
+    println!("1nd element: {:?}", iterator.next());
+    println!("2nd element: {:?}", iterator.next());
+    println!("3rd element: {:?}", iterator.next());
+    println!("4th element: {:?}", iterator.next());
+
+    print!("\nAll elements in user collection: ");
+    users.iter().for_each(|e| print!("{} ", e));
+
+    println!();
+}

behavioral/iterator/users.rs

@@ -0,0 +1,40 @@
+pub struct UserCollection {
+    users: [&'static str; 3],
+}
+
+impl UserCollection {
+    pub fn new() -> Self {
+        Self {
+            users: ["Alice", "Bob", "Carl"],
+        }
+    }
+
+    pub fn iter(&self) -> UserIterator {
+        UserIterator {
+            index: 0,
+            user_collection: self,
+        }
+    }
+}
+
+/// UserIterator allows sequential traversal through a complex users collection
+/// without exposing its internal details.
+pub struct UserIterator<'a> {
+    index: usize,
+    user_collection: &'a UserCollection,
+}
+
+// `Iterator` is a standard interface for dealing with iterators from the Rust standard library.
+impl Iterator for UserIterator<'_> {
+    type Item = &'static str;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index < self.user_collection.users.len() {
+            let user = Some(self.user_collection.users[self.index]);
+            self.index += 1;
+            return user;
+        }
+
+        None
+    }
+}