Rust 调用方法参考

Question

作为 Rust 的新手，我找到了很多关于这个问题的资源，但是 none 这确实可以帮助我。我想要做的是引用一个结构并调用它的方法。

最小化示例：

// A rather large struct I would want to live in the heap as to avoid copying it too often.
// Emulated by using a huge array for the sake of this example.
struct RatedCharacter {
    modifiers : [Option<f64>; 500000]
}

impl RatedCharacter {
    // A method of the large struct that also modifies it.
    fn get_rating(&mut self){
        self.modifiers[0] = Some(4.0);
        println!("TODO: GetRating");
    }
}

// A way to create an instance of the huge struct on the heap
fn create_rated_character(param1: f64, param2: f64) -> Box<RatedCharacter>{
    let modifiers : ModifierList = [None; 500000];
    do_initialisation_based_on_given_parameters();
    let result = RatedCharacter{
        modifiers : modifiers
    };
    return Box::new(result);
}

fn main() {
    let mybox : Box<RatedCharacter> = create_rated_character(2,4);
    let mychar : &RatedCharacter = mybox.as_ref();
    // The following line fails, as the borrow checker does not allow this.
    mychar.get_rating();
}

编译器抱怨cannot borrow '*mychar' as mutable, as it is behind a '&' reference。

如何让 RatedCharacter 的实例存在于堆上并仍然调用它的方法？

Answer 1

由于您的 get_rating 也令人惊讶地修改了实例，因此您需要使其可变。首先是 Box，然后是引用也应该是可变的。

    let mut mybox : Box<RatedCharacter> = create_rated_character(2 as f64,4 as f64);
    let mychar : &mut RatedCharacter = mybox.as_mut();

    mychar.get_rating();

Rust 调用方法参考

Rust call method on reference

rust

borrow-checker