Hands-on Rust: Chapter 7 Invalid Camera Method from Chapter 5

Community PragProg Customers
,
1

In the end of chapter 7 we write the movement function in movement.rs
We call the camera on_player_move method like so:

camera​.on_player_move​(&want_move.destination);

This results in a compile error on my machine because on_player_move expects a reference.

The latest code in the book I see for the camera method is back in Chapter 5

 	    ​pub​ ​fn​ ​on_player_move​(&​mut​ ​self​, player_position: Point) {
​ 	        ​self​.left_x = player_position.x ​-​ DISPLAY_WIDTH​/​2;
​ 	        ​self​.right_x = player_position.x + DISPLAY_WIDTH​/​2;
​ 	        ​self​.top_y = player_position.y ​-​ DISPLAY_HEIGHT​/​2;
​ 	        ​self​.bottom_y = player_position.y + DISPLAY_HEIGHT​/​2;
​ 	    }

Looking at the code zip it appears that the function is always expecting a reference, though I got a bit lost on the folder names so it could be wrong there too.

Changing the method to expect a reference fixes the compile error and it appears to run fine.

I didn’t test it but I think the method could take in either a Point or an &Point and as long as the method is called the same it should be fine? If this is true, is this because destination always is a calculated value that doesn’t need to worry about the borrow checker?

2 Likes