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boxing_todo

Instructions

The objective is to do an api to parse a list of todos that is organized in a JSON file, handling all possible errors in a multiple error system.

Organization of the JSON file:

{
    "title" : "TODO LIST FOR PISCINE RUST",
    "tasks": [
        { "id": 0, "description": "do this", "level": 0 },
        { "id": 1, "description": "do that", "level": 5 }
    ]
}

Create a module in another file called error.rs that handles the boxing of errors. This module must implement an enum called ParseErr that will take care of the parsing errors, it must have the following elements:

Empty
Malformed, that has a dynamic boxed error as element

A structure called ReadErr that will take care of the reading errors, having just an element called child_err of type Box<dyn Error>.

For each data structure you will have to implement a function called fmt for the trait Display that writes out the message "Fail to parse todo" in case it's a parsing error, otherwise it writes the message "Failed to read todo file". And for the Error trait the following functions:

description that returns a string literal that says:
- "Todo List parse failed: " for the ParseErr
- "Todo List read failed: " for the ReadErr.
cause that returns an Option with the error:
- For the ReadErr it must just return the option with the error
- For the ParseErr it will return an option that can be None if the tasks are empty otherwise the error, if the parsing is malformed.

In the lib file you will have to implement a function called get_todo that receives a string and returns a Result that can be the structure TodoList or a boxing error. This function must be able to deserialize the json file, basically it must parse and read the JSON file and return the TodoList if everything is fine otherwise the error.

Expected Function

For error.rs

use std::fmt;
use std::fmt::Display;
use std::error::Error;

pub enum ParseErr {
    // expected public fields
}

// required by error trait
impl Display for ParseErr {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    }
}

pub struct ReadErr {
    // expected public fields
}

// required by error trait
impl Display for ReadErr {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    }
}

impl Error for ReadErr {
    fn description(&self) -> &str {}
    fn cause(&self) -> Option<&dyn Error> {}
}

impl Error for ParseErr {
    fn description(&self) -> &str {}
    fn cause(&self) -> Option<&dyn Error> {}
}

for lib.rs

mod error;
use error::{ ParseErr, ReadErr };
use std::error::Error;
use serde::{ Deserialize, Serialize };

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct Task {
    id: u32,
    description: String,
    level: u32,
}

#[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
pub struct TodoList {
    title: String,
    tasks: Vec<Task>,
}

impl TodoList {
    pub fn get_todo(path: &str) -> Result<TodoList, Box<dyn Error>> {}
}

Usage

Here is a program to test your function. Note that you can create some todo list your self to test it, but you can find the JSON files that are being tested here

mod lib;
use lib::{ TodoList };

fn main() {
    let todos = TodoList::get_todo("todo.json");
    match todos {
        Ok(list) => println!("{:?}", list),
        Err(e) => {
            println!("{}{:?}", e.description(), e.cause());
        }
    }

    let todos = TodoList::get_todo("no_todo_list.json");
    match todos {
        Ok(list) => println!("{:?}", list),
        Err(e) => {
            println!("{}{:?}", e.description(), e.cause());
        }
    }

    let todos = TodoList::get_todo("malformed_object.json");
    match todos {
        Ok(list) => println!("{:?}", list),
        Err(e) => {
            println!("{}{:?}", e.description(), e.cause().unwrap());
        }
    }
}

And its output:

student@ubuntu:~/[[ROOT]]/test$ cargo run
TodoList { title: "TODO LIST FOR PISCINE RUST", tasks: [Task { id: 0, description: "do this", level: 0 }, Task { id: 1, description: "do that", level: 5 }] }
Todo List parse failed: None
Todo List parse failed: Malformed(Error("missing field `title`", line: 1, column: 2))
student@ubuntu:~/[[ROOT]]/test$

4.5 KiB Raw Blame History

boxing_todo

Instructions

Expected Function

Usage

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4.5 KiB

Raw Blame History