如何实现rustc

如何实现rustc_serialize :: Decodable的结构有一个字段值是另一个结构？(How to implement rustc_serialize::Decodable for struct that has a field value that is another struct?)

我需要为我的Herd结构实现rustc_serialize::Decoder特征：

extern crate chrono; extern crate rustc_serialize; use chrono::NaiveDate; use rustc_serialize::Decodable; struct Herd { id: i32, breed: String, name: String, purchase_date: NaiveDate, } impl Decodable for Herd { fn decode<D: Decoder>(d: &mut D) -> Result<Herd, D::Error> { d.read_struct("Herd", 4, |d| { let id = try!(d.read_struct_field("id", 0, |d| d.read_i32())); let breed = try!(d.read_struct_field("breed", 1, |d| d.read_str())); let name = try!(d.read_struct_field("name", 2, |d| d.read_str())); let purchase_date = try!(d.read_struct_field("purchase_date", 3, |i| { i.read_struct("NaiveDate", 1, |i| { let ymdf = try!(i.read_struct_field("ymdf", 0, |i| i.read_i32())); Ok(NaiveDate { ymdf: ymdf }) }) })); Ok(Herd { id: id, breed: breed, name: name, purchase_date: purchase_date, }) }) } }

我无法使用#[derive(RustcDecodable)]因为发生以下错误：

error[E0277]: the trait bound chrono::NaiveDate: rustc_serialize::Decodable is not satisfied
 
 我正在手动实现Decodable ，这就是你在上面的代码中看到的。 来自rust- NaiveDate crate的NaiveDate是一个具有数据类型为i32字段的结构。 
 
 当我现在运行代码时，我收到消息： 
 
 
 
 struct chrono :: NaiveDate的字段ymdf是私有的 
 
 
 我如何实现NaiveDate Decoder ？ 有一种更简单的方法来实现Decodable我的Herd结构？ 我是一个全能的初学者程序员; 也许有另一种方法来看待这个问题。 
 
 我正在使用Rust 1.12以下依赖项： 
 
 
  nickel = "0.9.0"  
  postgres = { version = "0.12", features = ["with-chrono"]}  
  chrono = "0.2"  
  rustc-serialize = "0.3"  
I need to implement the rustc_serialize::Decoder trait for my Herd struct:
 
extern crate chrono;
extern crate rustc_serialize;

use chrono::NaiveDate;
use rustc_serialize::Decodable;

struct Herd {
    id: i32,
    breed: String,
    name: String,
    purchase_date: NaiveDate,
}

impl Decodable for Herd {
    fn decode<D: Decoder>(d: &mut D) -> Result<Herd, D::Error> {
        d.read_struct("Herd", 4, |d| {
            let id = try!(d.read_struct_field("id", 0, |d| d.read_i32()));
            let breed = try!(d.read_struct_field("breed", 1, |d| d.read_str()));
            let name = try!(d.read_struct_field("name", 2, |d| d.read_str()));
            let purchase_date = try!(d.read_struct_field("purchase_date", 3, |i| {
                i.read_struct("NaiveDate", 1, |i| {
                    let ymdf = try!(i.read_struct_field("ymdf", 0, |i| i.read_i32()));
                    Ok(NaiveDate { ymdf: ymdf })
                })
            }));

            Ok(Herd {
                id: id,
                breed: breed,
                name: name,
                purchase_date: purchase_date,
            })
        })
    }
}
 
I'm unable to use #[derive(RustcDecodable)] because the following error occurs: 
 
error[E0277]: the trait bound chrono::NaiveDate: rustc_serialize::Decodable is not satisfied
 
I'm working on manually implementing Decodable and that's what you see in the code above. NaiveDate from the rust-chrono crate is a struct with one field that is of data type i32. 
 
When I run the code right now, I receive the message: 
 
 
 
field ymdf of struct chrono::NaiveDate is private
 
 
How do I implement Decoder for NaiveDate? Is there a simpler way to implement Decodable for my Herd struct? I am an all-around beginner programmer; perhaps there is another way to look at this problem.
 
I am using Rust 1.12 with the following dependencies:
 
 
 nickel = "0.9.0" 
 postgres = { version = "0.12", features = ["with-chrono"]} 
 chrono = "0.2" 
 rustc-serialize = "0.3" 

                
最满意答案
                
                    
                        
 NaiveDate确实实现了可Decodable但在可选功能"rustc-serialize" 。 
 
 您应该在您的Cargo.toml添加以激活它： 
 
chrono = { version = "0.2", features = ["rustc-serialize"]}
NaiveDate does implement Decodable but under an optional feature "rustc-serialize".
 
You should add this in your Cargo.toml to activate it:
 
chrono = { version = "0.2", features = ["rustc-serialize"]}