-This error occurs when an attempt is made to assign to a borrowed value.
+An attempt was made to assign to a borrowed value.
Erroneous code example:
num: u8,
}
-fn main() {
- let mut fancy_num = FancyNum { num: 5 };
- let fancy_ref = &fancy_num;
- fancy_num = FancyNum { num: 6 };
- // error: cannot assign to `fancy_num` because it is borrowed
+let mut fancy_num = FancyNum { num: 5 };
+let fancy_ref = &fancy_num;
+fancy_num = FancyNum { num: 6 };
+// error: cannot assign to `fancy_num` because it is borrowed
- println!("Num: {}, Ref: {}", fancy_num.num, fancy_ref.num);
-}
+println!("Num: {}, Ref: {}", fancy_num.num, fancy_ref.num);
```
Because `fancy_ref` still holds a reference to `fancy_num`, `fancy_num` can't
num: u8,
}
-fn main() {
- let mut fancy_num = FancyNum { num: 5 };
- let moved_num = fancy_num;
- fancy_num = FancyNum { num: 6 };
+let mut fancy_num = FancyNum { num: 5 };
+let moved_num = fancy_num;
+fancy_num = FancyNum { num: 6 };
- println!("Num: {}, Moved num: {}", fancy_num.num, moved_num.num);
-}
+println!("Num: {}, Moved num: {}", fancy_num.num, moved_num.num);
```
If the value has to be borrowed, try limiting the lifetime of the borrow using
num: u8,
}
-fn main() {
- let mut fancy_num = FancyNum { num: 5 };
-
- {
- let fancy_ref = &fancy_num;
- println!("Ref: {}", fancy_ref.num);
- }
+let mut fancy_num = FancyNum { num: 5 };
- // Works because `fancy_ref` is no longer in scope
- fancy_num = FancyNum { num: 6 };
- println!("Num: {}", fancy_num.num);
+{
+ let fancy_ref = &fancy_num;
+ println!("Ref: {}", fancy_ref.num);
}
+
+// Works because `fancy_ref` is no longer in scope
+fancy_num = FancyNum { num: 6 };
+println!("Num: {}", fancy_num.num);
```
Or by moving the reference into a function:
num: u8,
}
-fn main() {
- let mut fancy_num = FancyNum { num: 5 };
-
- print_fancy_ref(&fancy_num);
-
- // Works because function borrow has ended
- fancy_num = FancyNum { num: 6 };
- println!("Num: {}", fancy_num.num);
-}
-
fn print_fancy_ref(fancy_ref: &FancyNum){
println!("Ref: {}", fancy_ref.num);
}
+
+let mut fancy_num = FancyNum { num: 5 };
+
+print_fancy_ref(&fancy_num);
+
+// Works because function borrow has ended
+fancy_num = FancyNum { num: 6 };
+println!("Num: {}", fancy_num.num);
```