Lesson 5 bonus exercise

[Mitch Raful]

Hi, Michael,

In lesson 5, the section on std::fs::File, you leave appending to a file as a bonus exercise.  Here's my solution

extern crate gtk;

use gtk::prelude::*;
use std::fs::{File, OpenOptions};
use gtk::{Button, Window, WindowType};
use std::io::{Write, ErrorKind};


fn main() {
    if gtk::init().is_err() {
        println!("Failed to initialize GTK.");
        return;
    }

    let window = Window::new(WindowType::Toplevel);
    window.set_title("First GTK+ Program");
    window.set_default_size(350, 70);
    let button = Button::new_with_label("Click me!");
    window.add(&button);
    window.show_all();
    window.connect_delete_event(|_, _| {
        gtk::main_quit();
        Inhibit(false)
    });

    button.connect_clicked(|_| {
        write_me(b"I was clicked.\n")
            .expect("Problem writing to file.");
    });

    gtk::main();
}

fn write_me(line: &[u8; 15]) -> std::io::Result<()> {

    let mut file = OpenOptions::new()
        .append(true)
        .open("mylog.txt")
        .unwrap_or_else(|error| {
        if error.kind() == ErrorKind::NotFound {
            File::create("mylog.txt").unwrap_or_else(|error| {
                panic!("Problem creating file: {:?}", error);
            })
        } else {
            panic!("Can't open file: {:?}", error);
        }
    });
    file.write(line)
        .expect("Error writing to file!");
    Ok(())
}

Cheers,

Mitch