Rust-Programming-Language/C2/Ownership/English - Revision history

Madhurig at 09:58, 7 October 2025

2025-10-07T09:58:58Z

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Nirmala Venkat: Created page with "{| border="1" |- || '''Visual Cue''' || '''Narration''' |- || '''Slide 1''' || Welcome to the Spoken Tutorial on
2025-09-22T12:12:59Z

Created page with "{| border="1" |- || '''Visual Cue''' || '''Narration''' |- || '''Slide 1''' || <span style="color:#000000;">Welcome to the Spoken Tutorial on </span><span style="color:#000000..."

New page
{| border="1"
|-
|| '''Visual Cue'''
|| '''Narration'''
|-
|| '''Slide 1'''
|| <span style="color:#000000;">Welcome to the Spoken Tutorial on </span><span style="color:#000000;">'''Ownership</span> <span style="color:#000000;">in</span> <span style="color:#000000;">Rust.'''</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <div style="color:#000000;">'''Slide 2'''</div>

<div style="color:#000000;">'''Learning Objectives'''</div>
|| In this tutorial, we will learn about:
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">Ownership</div>
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">Ownership Rules</div>
* <div style="margin-left:1.27cm;margin-right:0cm;"><span style="color:#000000;">Drop and Copy </span>traits</div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <div style="color:#000000;">'''Slide 3'''</div>

<div style="color:#000000;">'''System Requirements'''</div>
|| <span style="color:#000000;">To record this tutorial </span>I am<span style="color:#000000;"> using:</span>
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">Ubuntu Linux OS version 22.04</div>
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">Rust version 1.80.0 </div>
* <div style="margin-left:1.27cm;margin-right:0cm;"><span style="color:#000000;">Visual Studio Code v</span>ersion<span style="color:#000000;"> 1.19.0</span></div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <div style="color:#000000;">'''Slide 4'''</div>

<div style="color:#000000;">'''Prerequisites'''</div>
|| <span style="color:#000000;">To follow this tutorial, you should be familiar with compiling and running a </span><span style="color:#000000;">'''Rust'''</span><span style="color:#000000;"> program.</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide'''</span><span style="color:#000000;"> </span><span style="color:#000000;">'''5'''</span>

<div style="color:#000000;">'''Code Files'''</div>
||
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">The following code file is required to practise this tutorial.</div>
* <div style="margin-left:1.27cm;margin-right:0cm;">Ownership.rs</div>
* <div style="margin-left:1.27cm;margin-right:0cm;"><span style="color:#000000;">This file is provided in the </span><span style="color:#000000;">'''Code Files'''</span><span style="color:#000000;"> link of this tutorial page.</span></div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <div style="color:#000000;">'''Slide 6'''</div>

<div style="color:#000000;">'''Ownership'''</div>
|| Let us now learn about''' Ownership.'''

* <div style="margin-left:1.27cm;margin-right:0cm;"><span style="color:#000000;">'''Ownership'''</span><span style="color:#000000;"> allows memory safety without a garbage collector.</span></div>
* <div style="color:#171717;margin-left:1.27cm;margin-right:0cm;">It is a key feature of the Rust language that allows it to be both safe and fast.</div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide</span> 7'''

<div style="color:#000000;">'''Ownership Rules'''</div>
||
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">Each value in Rust has a single owner</div>
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">There can be only one owner at a time</div>
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">When the owner goes out of scope the value will be dropped.</div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide</span> 8'''

<div style="color:#000000;">'''Drop trait'''</div>
||
* <div style="color:#000000;margin-left:1.27cm;margin-right:0cm;">To understand the ownership rules, we need to note two traits: </div>
<span style="color:#000000;">'''drop '''</span><span style="color:#000000;">and</span><span style="color:#000000;">''' copy'''</span>
<div style="margin-left:1.27cm;margin-right:0cm;"><span style="color:#000000;">The</span>se traits are <span style="color:#000000;">fundamental traits related to resource management and memory handling.</span></div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.101cm;padding-right:0.191cm;"
| style="color:#000000;" |
|| <span style="color:#000000;">Let us </span>understand the '''drop'''<span style="color:#000000;"> trait through an example.</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">Open </span><span style="color:#000000;">'''Visual'''</span><span style="color:#000000;"> </span><span style="color:#000000;">'''code editor'''</span>
|| <span style="color:#000000;">Open the </span><span style="color:#000000;">'''Visual </span>S<span style="color:#000000;">tudio code editor.'''</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">In the menu bar, click on </span><span style="color:#000000;">'''Terminal'''</span><span style="color:#000000;"> and select</span><span style="color:#000000;">''' New Terminal'''</span><span style="color:#000000;">.</span>

|| <span style="color:#000000;">In the menu bar, click on </span><span style="color:#000000;">'''Terminal'''</span><span style="color:#000000;"> and select</span><span style="color:#000000;">''' New Terminal'''</span><span style="color:#000000;">.</span>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''> cd'''</span><span style="color:#000000;"> </span><span style="color:#000000;">'''Desktop'''</span><span style="color:#000000;">/</span><span style="color:#000000;">'''MyRustProject'''</span>

<span style="color:#000000;">'''>'''</span><span style="color:#000000;"> </span><span style="color:#000000;">'''cargo new </span>Ownership'''

<div style="color:#000000;">'''In the menu bar, File >> Open folder >> Desktop >> MyRustProject >> Ownership'''</div>
|| <span style="color:#000000;">Let us go to our working directory </span><span style="color:#000000;">'''MyRustProject'''</span><span style="color:#000000;"> as explained earlier.</span>

<span style="color:#000000;">Type the command </span><span style="color:#000000;">'''cargo new Ownership</span> '''<span style="color:#000000;">and press </span><span style="color:#000000;">'''Enter.'''</span>

<div style="color:#000000;">Open the created project as shown.</div>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">Point to the </span><span style="color:#000000;">'''main.rs'''</span><span style="color:#000000;"> file.</span>

|| <span style="background-color:#ffffff;color:#000000;">In the </span><span style="background-color:#ffffff;color:#000000;">'''main.rs '''</span><span style="background-color:#ffffff;color:#000000;">file, copy and paste the code from the </span><span style="background-color:#ffffff;color:#000000;">'''Code file'''</span><span style="background-color:#ffffff;color:#000000;">.</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <div style="color:#000000;">struct MyStruct {</div>

<div style="color:#000000;">data: String,</div>

<div style="color:#000000;">}</div>

<span style="color:#000000;">//highlight impl Drop for MyStruct</span><span style="color:#000000;">''' '''</span>

<div style="color:#000000;">impl Drop for MyStruct {</div>

<div style="color:#000000;">fn drop(&mut self) {</div>

<div style="color:#000000;">println!("Dropping MyStruct with data: {}", self.data);</div>

<div style="color:#000000;">}</div>

<div style="color:#000000;">}</div>

<div style="color:#000000;">fn main() {</div>

<div style="color:#000000;">println!("Start");</div>

<div style="color:#000000;">{</div>

<div style="color:#000000;">let new_struct = MyStruct {</div>

<div style="color:#000000;">data: String::from("Hello, world!"),</div>

<div style="color:#000000;">};</div>

<div style="color:#000000;">}</div>

<div style="color:#000000;">println!("End");</div>

<div style="color:#000000;">// my_struct goes out of scope here, and the drop method is called.</div>

<div style="color:#000000;">}</div>
|| This code explains how '''ownership '''and''' Drop trait''' work together in Rust.

<span style="background-color:#ffffff;color:#000000;">Here we </span><span style="color:#000000;">created a </span><span style="color:#000000;">'''struct'''</span><span style="color:#000000;"> </span><span style="color:#000000;">'''MyStruct'''</span><span style="color:#000000;"> which contains data of </span><span style="color:#000000;">'''string'''</span><span style="color:#000000;"> type</span>.

<span style="color:#000000;">In the implementation block, </span>the''' drop'''<span style="color:#000000;"> trait for </span><span style="color:#000000;">'''Mystruct'''</span><span style="color:#000000;"> has been implemented.</span>

<span style="color:#000000;">The drop method is automatically called when an object </span><span style="color:#000000;">goes out of scope.</span>

<span style="color:#000000;">In the main program, </span><span style="color:#000000;">'''new_struct'''</span><span style="color:#000000;"> is created with "</span><span style="color:#000000;">'''Hello, world!"'''</span><span style="color:#000000;"> stored in its data.</span>

<span style="color:#000000;">Here, </span><span style="color:#000000;">'''new_struct'''</span><span style="color:#000000;"> </span><span style="color:#000000;">owns </span><span style="color:#000000;">that string.</span>

<span style="color:#000000;">At the end of the inner scope, </span><span style="color:#000000;">'''new_struct '''</span><span style="color:#000000;">goes out of scope.</span>

<span style="color:#000000;">Rust </span><span style="color:#000000;">automatically calls</span><span style="color:#000000;"> </span><span style="color:#000000;">'''drop(&mut self)'''</span><span style="color:#000000;"> for </span><span style="color:#000000;">'''new_struct.'''</span>

In this code,''' drop''' happens before "End" is printed.

This is because the '''struct’'''s scope ends earlier.

Save the program.
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
||
|| Run the code to see the output.
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
||
|| <span style="color:#000000;">Next, let us see an example of a </span><span style="color:#000000;">'''copy'''</span><span style="color:#000000;"> trait.</span>

<span style="color:#000000;">Clear the code window and copy paste the code from the </span>'''C<span style="color:#000000;">ode file'''</span><span style="color:#000000;">.</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <div style="color:#252525;">fn main() {</div>

<div style="color:#252525;">let x = 10;</div>

<div style="color:#252525;">let y = x; // x is copied, not moved</div>

<div style="color:#252525;">println!("x: {}, y: {}", x, y); // x is still accessible</div>

<div style="color:#252525;">let s = String::from("Hello world");</div>

<span style="color:#252525;">let </span><span style="color:#252525;">v</span><span style="color:#252525;"> = s; // Move occurs, `s` is no longer valid</span>

<div style="color:#252525;">// println!("{}", s); // This would cause an error</div>

<div style="color:#252525;">}</div>

|| <div style="color:#252525;">Here, x is assigned a value 10, and y is assigned to variable x. </div>

<span style="color:#000000;">For simple types like i32, bool, char, etc., Rust </span><span style="color:#000000;">'''copies'''</span><span style="color:#000000;"> the value instead of moving it.</span>

<span style="color:#000000;">These data types are entirely stored on the </span><span style="color:#000000;">'''stack. '''</span>

<div style="color:#000000;">It has a fixed size known at compile time.</div>

<span style="color:#000000;">After copying, both</span><span style="color:#000000;">''' x'''</span><span style="color:#000000;"> and</span><span style="color:#000000;">''' y '''</span><span style="color:#252525;">hold the value 10.</span>

<span style="color:#252525;">But for the string, the variable </span><span style="color:#252525;">''s''</span><span style="color:#252525;"> is assigned the value “Hello World!”.</span>

Variable '''v '''is assigned to '''s.'''

<span style="color:#252525;">Here, </span><span style="color:#252525;">copy doesn’t happen because of </span><span style="color:#252525;">'''String'''</span><span style="color:#252525;"> being an owned type. </span>

<span style="color:#252525;">This fails because after the move, </span><span style="color:#252525;">'''s '''</span><span style="color:#252525;">no longer owns any valid data.</span>

<span style="color:#000000;">Rust’s compiler prevents you from using </span><span style="color:#000000;">'''s '''</span><span style="color:#000000;">here.</span>

<div style="color:#252525;">Hence it would show an error.</div>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
| style="color:#000000;" |
|| Run the code to see the output.

<span style="color:#000000;">We can see the copy trait is implemented by default for </span><span style="color:#000000;">'''integer'''</span><span style="color:#000000;">.</span>

<span style="color:#000000;">For string type we </span>get<span style="color:#000000;"> an error.</span>

<span style="color:#252525;">Types like </span><span style="color:#252525;">'''String'''</span><span style="color:#252525;"> or other heap-allocated structures do not implement </span><span style="color:#252525;">'''Copy'''</span><span style="color:#252525;"> by default.</span>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <div style="color:#000000;">let t = s.clone(); // deep copy of the string data</div>

<span style="color:#000000;">println!("s: {}, </span>v<span style="color:#000000;">: {}", s, </span>v<span style="color:#000000;">); // both accessible</span>
|| We can use the '''clone''' method to solve this issue.

Let's add the clone method as '''s.clone() '''in the code.

'''.clone() '''makes an '''explicit''' deep copy of the heap data.

Change the print statement to print '''s '''and''' v .'''

Save the program.
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
| style="color:#000000;" |
|| Run the code to see the correct output.
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide </span>9'''

<span style="color:#000000;">'''Summary'''</span>
|| <div style="color:#000000;">This brings us to the end of this tutorial.</div>

<div style="color:#000000;">Let us summarize. </div>
|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide </span>10'''

<div style="color:#000000;">'''Assignment'''</div>
|| As an assignment. write a program that:
* <div style="margin-left:1.27cm;margin-right:0cm;">Creates a String variable called '''greeting''' with the value "Hello, Rust!".</div>
* <div style="margin-left:1.27cm;margin-right:0cm;">Passes it to a function '''takes_ownership''' that prints the value.</div>
* <div style="margin-left:1.27cm;margin-right:0cm;">Inside this function, remember that ownership is moved.</div>

|- style="border:1pt solid #000000;padding-top:0cm;padding-bottom:0cm;padding-left:0.206cm;padding-right:0.191cm;"
|| <span style="color:#000000;">'''Slide </span>11'''

<div style="color:#000000;">'''Thank You'''</div>
|| Thank you for joining
|-
|}
<div style="margin-left:-1.588cm;margin-right:-1.429cm;"></div>