对于指针，一个区别是需要在析构之时会解除引用 ，因为它们使用不同的概念，如C语言。
*
&, ref, 和 ref mut
fn main() {
// Assign a reference of type `i32`. The `&` signifies there
// is a reference being assigned.
let reference = &4;
match reference {
// If `reference`s is pattern matched against `&val`, it results
// in a comparison like:
// `&i32`
// `&val`
// ^ We see that if the matching `&`s are dropped, then the `i32`
// should be assigned to `val`.
&val => println!("Got a value via destructuring: {:?}", val),
}
// To avoid the `&`, you dereference before matching.
match *reference {
val => println!("Got a value via dereferencing: {:?}", val),
}
// What if you don't start with a reference? `reference` was a `&`
// because the right side was already a reference. This is not
// a reference because the right side is not one.
let _not_a_reference = 3;
// Rust provides `ref` for exacty this purpose. It modifies the
// assignment so that a reference is created for the element; this
// reference is assigned.
let ref _is_a_reference = 3;
// Accordingly, by defining 2 values without references, references
// can be retrieved via `ref` and `ref mut`.
let value = 5;
let mut mut_value = 6;
// Use `ref` keyword to create a reference.
match value {
ref r => println!("Got a reference to a value: {:?}", r),
}
// Use `ref mut` similarly.
match mut_value {
ref mut m => {
// Got a reference. Gotta dereference it before we can
// add anything to it.
*m += 10;
println!("We added 10. `mut_value`: {:?}", m);
},
}
} 