1 files changed, 68 insertions, 0 deletions
diff --git a/rust/borrowing.rs b/rust/borrowing.rs
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+++ b/rust/borrowing.rs
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+// Borrowing data
+//
+// We can access data created in another scope by borrowing it.
+//
+// Can be borrowed mutable or immutable.
+//
+// Borrowing Rules:
+//
+// - At any given time, you can have either a
+//      SINGLE MUTABLE reference or
+//      MANY IMMUTABLE references
+// - References must always be valid
+//
+
+// We can define references by
+//
+// Passing the reference to a var:  let x = &var
+// Using the ref keyworkd like:     let ref x = var
+
+fn main() {
+    let s1 = String::from("hello");
+
+    // Pass a reference to String s1
+    // this is a reference to the s1 not the string per se
+    let len: usize = calculate_length(& s1);
+
+    // Mutable ref
+    let mut c = String::from("Howdy");
+
+    // Pass a mutable reference to change function
+    change(&mut c);
+
+    // We can still use s1 here, because s1 is still the owner.
+    println!("The length of '{}' is {}.", s1, len);
+    println!("{}", c);
+
+    print_pointer();
+}
+
+
+// The function receives a 'reference' to a String
+fn calculate_length(s: & String) -> usize {
+    return s.len();
+}
+
+fn change(c: &mut String) {
+    c.push_str(" partner");
+}
+
+fn print_pointer() {
+    let x: i32 = 5;
+
+    let p: &i32 = &x;
+
+    println!("PTR is: {:p}", p);
+}
+// This function is just an example of 2nd rule violation
+// It returns a reference to a string that will run out of
+// scope once the function returns.
+// Thanks to that, we return a dangling pointer. Rustc won't
+// let us compile it.
+
+// Could be fixed by returning the String data itself
+//fn dangling_ptr() -> &String {
+//    let s = String::from("howdy");
+//
+//    return &s;
+//}