result_test.rs

// #1 version without Result as return type
fn from_json(data: &str) -> humans::Humans {
    let mut humans = Vec::new();

    let msg: Value = serde_json::from_str(data).expect("json error");
    for human in msg["people"].as_array().unwrap().iter() {
        humans.push(humans::Human::new(
            human["name"].as_str().unwrap(),
            human["craft"].as_str().unwrap(),
        ));
    }

    humans
}

/****************************************************************/

// #2 i guess i do it wrong

fn from_json(data: &str) -> Result<humans::Humans, String> {
    let mut humans = Vec::new();
    match serde_json::from_str(data) {
        Ok(msg) => {
            let msg : Value = msg;
            match msg["people"].as_array() {
                Some(people) => {
                    for person in people.iter() {
                        match person["name"].as_str() {
                            Some(name) => {
                                match person["craft"].as_str() {
                                    Some(craft) => {
                                        humans.push(humans::Human::new(name, craft));
                                    },
                                    None => {
                                        return Err(String::from("'craft' field is missing"));
                                    }
                                }
                            },
                            None => {
                                return Err(String::from("'name' field is missing"));
                            }
                        }
                    }
                },
                None => {
                    return Err(String::from("'people' field is missing"));
                }
            }
        },
        Err(reason) => {
            return Err(String::from("Unable to deserialize json data: ") + reason.description());
        }
    }
    Ok(humans)
}


/****************************************************************/

// #3 maybe better?

fn from_json(data: &str) -> Result<humans::Humans, String> {
    let mut humans = Vec::new();

    let msg: Value = match serde_json::from_str(data) {
        Ok(msg) => msg,
        Err(reason) => {
            return Err(String::from("Unable to deserialize json data: ") + reason.description())
        }
    };

    let people = match msg["people"].as_array() {
        Some(people) => people,
        None => return Err(String::from("'people' field is missing")),
    };

    for person in people.iter() {
        let name = match person["name"].as_str() {
            Some(name) => name,
            None => return Err(String::from("'name' field is missing")),
        };

        let craft = match person["craft"].as_str() {
            Some(craft) => craft,
            None => return Err(String::from("'craft' field is missing")),
        };

        humans.push(humans::Human::new(name, craft));
    }

    Ok(humans)
}