Add ownership example

Author: chanakaudaya

ownership/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "ownership"
+version = "0.1.0"
+authors = ["Chanaka Fernando <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

ownership/src/main.rs

@@ -0,0 +1,98 @@
+fn main() {
+    println!("Hello, ownership!");
+
+    let mut s = String::from("hello");
+    s.push_str(", world!");
+
+    println!("{}", s);
+
+    let s1 = String::from("Chanaka");
+    // Cloning the data here because RUST does not allow accessing s1 after moving the ownership to s2
+    let s2 = s1.clone();
+
+    println!("s1 is {} and s2 is {}", s1, s2);
+    int_copy();
+
+    let a = String::from("Hello");
+    takes_ownership(a);
+    // The below line does not work because the ownership of "a" has been transferred to takes_ownership function
+    //println!("{} World!", a);
+
+    let b = 5;
+    makes_copy(b);
+    println!("{} World!", b);
+
+    let s1 = gives_ownership();
+    let s2 = String::from("hello");
+    let s3 = takes_and_gives_back(s2);
+
+    let n = calculate_length(&s1);
+    println!("The length of string {} is {}", s1, n);
+
+    let mut s = String::from("hello");
+    change(&mut s);
+    println!("Mutated string is {}", s);
+
+    let my_string = String::from("hello world");
+
+    // first_word works on slices of `String`s
+    let word = first_word(&my_string[..]);
+
+    let my_string_literal = "hello world";
+
+    // first_word works on slices of string literals
+    let word = first_word(&my_string_literal[..]);
+
+    // Because string literals *are* string slices already,
+    // this works too, without the slice syntax!
+    let word = first_word(my_string_literal);
+
+    println!("first word is {}", word);
+
+}
+
+fn int_copy() {
+    println!("Starting the integer copy function");
+    let x = 5; 
+    // Here we don't use clone since types stored in stack does not need the clone method
+    let y = x;
+    println!("The value of x is {}, the value of y is {}", x, y);
+}
+
+fn takes_ownership(some_string: String) {
+    println!("{}", some_string);
+}
+
+fn makes_copy(some_integer: i32) {
+    println!("{}", some_integer);
+}
+
+fn gives_ownership() -> String {
+    let some_string = String::from("hello");
+    println!("from gives ownership {}", some_string);
+    some_string
+}
+
+fn takes_and_gives_back(a_string: String) -> String {
+    println!("from takes and gives back {}", a_string);
+    a_string
+}
+
+fn calculate_length(s: &String) -> usize {
+    s.len()
+}
+
+fn change(some_string: &mut String) {
+    some_string.push_str(", world");
+}
+
+fn first_word(s: &str) -> &str {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[0..i];
+        }
+    }
+    &s[..]
+}