rust - 如何重用结构的公共(public)代码？

Question

我想为结构重用代码。例如:

use std::fmt::Display;

struct CommonStruct<T: Display> {
    // could have more fields
    data: T
}

struct A<T: Display> {
    com: CommonStruct<T>,
    age: i32
}

struct B<T: Display> {
    com: CommonStruct<T>,
    name: String
}

impl<T: Display> A<T> {
    // could be more common functions
    fn print_data(&self) {
        // could be more complicated
        println!("data: {}", self.com.data);
    }
}

impl<T: Display> B<T> {
    // could be more common functions
    fn print_data(&self) {
        // could be more complicated
        println!("data: {}", self.com.data);
    }
}

fn main() {
    let a = A{ com: CommonStruct{data: 10}, age: 0 };
    a.print_data();
    let b = B{ com: CommonStruct{data: 12}, name: "123".to_string() };
    b.print_data();
}

其中 A 和 B 有一些由 CommonStruct 封装的公共(public)字段和一些公共(public)函数(例如，print_data ).

我尝试使用 trait 但找不到解决方案:

use std::fmt::Display;

struct CommonStruct<T: Display> {
    // could have more fields
    data: T
}

struct A<T: Display> {
    com: CommonStruct<T>,
    age: i32
}

struct B<T: Display> {
    com: CommonStruct<T>,
    name: String
}

trait Common {
    // could be more common functions
    fn print_data(&self) {
        print_data(&self)
    }
}

impl<T: Display> Common for A<T> {
}

impl<T: Display> Common for B<T> {
}

fn print_data(t: &Common) {
    // could be more complicated
    println!("data: {}", t.com.data);
}

fn main() {
    let a = A{ com: CommonStruct{data: 10}, age: 0 };
    a.print_data();
    let b = B{ com: CommonStruct{data: 12}, name: "123".to_string() };
    b.print_data();
}

Answer 1

由于 print_data 只使用了 CommonStruct，A 和 B 没有共享其他字段，所以将其作为 CommonStruct 的实现并直接调用它。

impl <T: Display> CommonStruct<T> {
    fn print_data(&self) {
        println!("data: {}", self.data);
    }
}

fn main() {
    let a = A{ com: CommonStruct{data: 10}, age: 0 };
    a.com.print_data();
    let b = B{ com: CommonStruct{data: 12}, name: "123".to_string() };
    b.com.print_data();
}

---

或者，创建一个具有 print_data 的具体实现的特征，它依赖于获取数据的方法。

trait HasData<T: Display> {
    fn get_data(&self) -> &T;
    fn print_data(&self) {
        // could be more complicated
        println!("data: {}", self.get_data());
    }
}

然后每个人只需要实现如何获取数据。

impl<T: Display> HasData<T> for CommonStruct<T> {
    fn get_data(&self) -> &T {
        return &self.data;
    }
}

impl<T: Display> HasData<T> for A<T> {
    fn get_data(&self) -> &T {
        return &self.com.data;
    }
}

impl<T: Display> HasData<T> for B<T> {
    fn get_data(&self) -> &T {
        return &self.com.data;
    }
}

fn main() {
    let a = A{ com: CommonStruct{data: 1}, age: 0 };
    a.print_data();
    let b = B{ com: CommonStruct{data: 2}, name: "123".to_string() };
    b.print_data();
    let c = CommonStruct{data: 3};
    c.print_data();
}