I just spent an hour searching for how I could have gotten an

Uncaught TypeError: Cannot set properties of null

javascript. I checked the spelling of the element whose property I was trying to set and knew that element wasn't null because the spelling was the same in the code as in the HTML. I also knew my element was loading, so it wasn't that either.

Turns out no, the element was null. I was trying to set " NameHere" when the element's actual name was "NameHere".

Off by a single space. No wonder I thought the spelling was the same—because all the non-whitespace was identical. (No, the quotation marks slanting in the second NameHere and being totally vertical in the first NameHere wasn't a part of the error, I am typing them all vertical and either Lemmy or my instance is "correcting" them to slanted for the second NameHere. But that is also another tricky-to-spot text difference to watch out for!)

And what did not help is that everywhere I specifically typed things out, I had it correct with no extra spaces. Trying to set " NameHere" was the result of modifying a bunch of correct strings, remembering to account for a comma I put between them, but not remembering to account for the space I added after the comma. In short, I only ever got to see " NameHere" written out in the debugger (which is how I caught it after like 30 repeats of running with the debugger), because everywhere I had any strings written out in the code or the HTML it was always written "NameHere".

I figured I'd post about it here in case I can help anyone else going crazy over an error they did not expect and cannot figure out. Next time I get a similar error I will not just check spelling, I'll check everything in the name carefully, especially whitespace at the beginning and end, or things one space apart being written with two spaces instead. Anyone else have a similar story to save the rest of us some time?

I understand the basic principle but I have trouble determining what is the hard line separating responsibilities of a Repository or a Service. I'm mostly thinking in terms of c# .NET in the following example but I think the design pattern is kinda universal.

Let's say I have tables "Movie" and "Genre". A movie might have multiple genres associated with it. I have a MovieController with the usual CRUD operations. The controller talks to a MovieService and calls the CreateMovie method for example.

The MovieService should do the basic business checks like verifying that the movie doesn't already exist in the database before creating, if all the mandatory fields are properly filled in and create it with the given Genres associated to it. The Repository should provide access to the database to the service.

It all sounds simple so far, but I am not sure about the following:

• which layer should be responsible for column filtering? if my Dto return object only returns 3 out of 10 Movie fields, should the mapping into the return Dto be done on the repository or service layer?

• if I need to create a new Genre entity while creating a new movie, and I want it to all happen in a single transaction, how do I do that if I have to go through MovieRepository and GenreRepository instead of doing it in the MovieService in which i don't have direct access to the dbcontext (and therefore can't make a transaction)?

• let's say I want to filter entries specifically to the currently logged in user (every user makes his own movie and genre lists) - should I filter by user ID in the MovieService or should I implement this condition in the repository itself?

• is the EF DbContext a repository already and maybe i shouldn't make wrappers around it in the first place?

Any help is appreciated. I know I can get it working one way or another but I'd like to improve my understanding of modern coding practices and use these patterns properly and efficiently rather than feeling like I'm just creating arbitrary abstraction layers for no purpose.

Alternatively if you can point me to a good open source projects that's easy to read and has examples of a complex app with these layers that are well organized, I can take a look at it too.

Besides some of the very, very obvious (don't copy/paste 100 lines of code, make it a function! Write comments for your future self who has forgotten this codebase 3 years from now!), I'm not sure how to write clean, efficient code that follows good practices.

In other words, I'm always privating my repos because I'm not sure if I'm doing some horrible beginner inefficiency/bad practice where I should be embarrassed for having written it, let alone for letting other people see it. Aside from https://refactoring.guru, where should I be learning and what should I be learning?

So I have struggled with classes and objects but think I'm starting to get it...? As part of a short online class I made a program that asked a few multiple choice questions and returns a score. To do this there are a few parts.

1. Define some inputs as lists of strings ((q, a), (q2, a2),...). The lists contain the questions and answers. This will be used as input and allows an easy way to change questions, add them, whatever.

2. Create a class that takes in the list and creates objects - the objects are a question and it's answer.

3. Create a new list that uses that class to store the objects.

4. Define a function that iterates over the list full of question/answer objects, and then asks the user the questions and tallies the score.

Number 2 is really what I am wondering about, is that generally what a class and object are? I would use an analogy of a factory being a class. It takes in raw materials (or pre-made parts) and builds them into standard objects. Is this a reasonable analogy of what a class is?

Let's say I am making an app that has table Category and table User. Each user has their own set of categories they created for themselves. Category has its own Id identity that is auto-incremented in an sqlite db.

Now I was thinking, since this is the ID that users will be seeing in their url when editing a category for example, shouldn't it be an ID specific only to them? If the user makes 5 categories they should see IDs from 1 to 5, not start with 14223 or whichever was the next internal ID in the database. After all when querying the data I will only be showing them their own categories so I will always be filtering on UserId anyway.

So let's say I add a new column called "UserSpecificCategoryId" or something like that - how do I make sure it is autogenerated in a safe way and stays unique per user? Do I have to do it manually in the code (which sounds annoying), use some sort of db trigger (we hate triggers, right?) or is this something I shouldn't even be bothering with in the first place?

Just started as in, I'm about an hour into a 4 hour intro video. Seeing two basic ways of manipulating things and don't understand the difference.

If I want to know the length of a string and I just guess at how to do it I would try one of these two things,

1. Len(string)
2. string.len()

What is the difference between these types of statements? How do I think about this to know which one I should expect to work?

I am really struggling to include proper testing practices into my code and would appreciate any advice on how to get going. I work in web dev so my I am interested in how to properly implement a suite of tests for websites and incorporate into it a CI/CD pipeline.

I find a lot of tutorials teach the most basic types of unit tests, 90% of the time most instructors teach how to write a test to sum two numbers, but when it comes to writing real unit test I find it hard to know what I should be testing. I learnt some cypress and have gotten better at including end-to-end testing because that makes more sense to me, but I still feel I am way short of where I should be.

How can I move forward? Did anyone else find themselves in my situation and find good resources to help them learn? Thx

I asked some LLM chatbots to give me some silly ideas to try. Below are a few of my favorite responses.

From Perplexity.ai

Six Degrees of Wikipedia: Creating a program that finds the shortest path between two random Wikipedia articles using graph traversal algorithms. This applies graph theory concepts to explore connections in a large knowledge base.

Emoji Encryption: Using hash tables and cryptographic algorithms to create an encryption system that converts text to emojis. This could be an interesting way to explore cryptography concepts in a fun, visual way.

From Gemini.google.com

Procrastination Station: This website creates increasingly elaborate and ridiculous tasks to distract you from what you actually need to do. Dishes? Nah, fold your socks into origami cranes!

Dramatic Password Validator: Forget boring error messages. This program rejects weak passwords with Shakespearean insults or movie villain monologues.

From Chatgpt.com

3. Time Travel Email Service: Build a data structure that allows you to send emails to yourself in the past, with time complexity considerations that are totally ignored because it’s time travel.

4. Mood-Driven Random Number Generator: Implement an algorithm that generates random numbers based on the mood of the user, using sentiment analysis on real-time facial expressions.

Hello, I would like to store these http headers in classes:

Host: developer.mozilla.org
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:50.0) Gecko/20100101 Firefox/50.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://developer.mozilla.org/testpage.html
Connection: keep-alive
Upgrade-Insecure-Requests: 1
If-Modified-Since: Mon, 18 Jul 2016 02:36:04 GMT
If-None-Match: "c561c68d0ba92bbeb8b0fff2a9199f722e3a621a"
Cache-Control: max-age=0

As you can see, many have unique data (numbers, strings, list of strings). I would like to:

• store a header name
• store list of possible options for that header (or store if it's a number)
• read an input header and store and return the found option / list of options / number
• make adding new types of headers as easy as possible

Is making hard coded classes for every type of header viable? How would this be done in the cleanest way possible?

The project home page.

The Github

Looks just like VS Code and I think it's still built on electron so take that as you will.

I'm trying to make minesweeper using rust and bevy, but it feels that my code is bloated (a lot of for loops, segments that seem to be repeating themselves, etc.)

When I look at other people's code, they are using functions that I don't really understand (map, zip, etc.) that seem to make their code faster and cleaner.

I know that I should look up the functions that I don't understand, but I was wondering where you would learn stuff like that in the first place. I want to learn how to find functions that would be useful for optimizing my code.

When resizing an X11 window with OpenGL content, the image becomes garbled and certain parts of the window, usually at the parts that wasn't originally part of the initial framebuffer.

I couldn't find any documentation on if I supposed to call some extra functions when the window is being resized or not. I otherwise process that even as a system event, so it can be further processed by the program using my API.

I'm writing a specification for a web app that will store sensitive user data, and the stakeholder asked that I consider a number of fairly standard security practices, but also including that the data be "encrypted at rest", i.e. so that if someone gains physical access to the hard disk at some later date the user data can't be retrieved.

The app is to be Node/Express on a VPS (probably against sqlite3), so since I would be doing that using an environmental variable stored in a file on that same computing instance, is that really providing any extra security?

I guess cloud big boys would be using key management systems to move the key off the local instance, and I could replicate that by using (Hashicorp Vault?) or building a service to keep the key elsewhere, but then I'd need secure access to that service, which once again would involve a key being stored locally.

What's your thoughts, experience, or usual practice around this?

I'm working on a little gui app that will eventually (hopefully) add a watermark to a photo. But right now I'm focused on just messing around with tkinter and trying to get some basic functionality down.

I've managed to display an image. Now I want to change the image to whatever is in the Entry widget (ideally, the user would put an absolute path to an image and nothing else). When I click the button, it makes the image disappear. I made it also create a plain text label to see if that would show up. It did.

Okay, time to break out the big guns. Add a breakpoint. py -m pdb main.py. it works. wtf?

def change_image():
    new_image = Image.open(image_path.get()).resize((480, 270))
    new_tk_image = ImageTk.PhotoImage(new_image)
    test_image_label.configure(image=new_tk_image)
    breakpoint()

with the breakpoint, the button that calls change_image works as expected. But without the breakpoint, it just makes the original image disappear. Please help me understand what is happening!

edit: all the code

import io
import tkinter as tk
from pathlib import Path
from tkinter import ttk

from PIL import ImageTk
from PIL import Image

from LocalImage import Localimage
from Layout import Layout

class State:
    def __init__(self) -> None:
        self.chosen_image_path = ""

    def update_image_path(self):
        self.chosen_image_path = image_path.get()



def change_image():
    new_image = Image.open(image_path.get()).resize((480, 270))
    new_tk_image = ImageTk.PhotoImage(new_image)
    test_image_label.configure(image=new_tk_image)
    breakpoint()

TEST_PHOTO_PATH = "/home/me/bg/space.png"
PIL_TEST_PHOTO_PATH = "/home/me/bg/cyberpunkcity.jpg"
pil_test_img = Image.open(PIL_TEST_PHOTO_PATH).resize((480,270))
# why does the resize method call behave differently when i inline it
# instead of doing pil_test_img.resize() on a separate line?


root = tk.Tk()

root.title("Watermark Me")
mainframe = ttk.Frame(root, padding="3 3 12 12")
mainframe.grid(column=0, row=0, sticky="NWES")

layout = Layout(mainframe)

image_path = tk.StringVar()
tk_image = ImageTk.PhotoImage(pil_test_img)
test_image_label = ttk.Label(image=tk_image)

entry_label = ttk.Label(mainframe, text="Choose an image to watermark:")
image_path_entry = ttk.Entry(mainframe, textvariable=image_path)
select_button = ttk.Button(mainframe, text="Select",
                           command=change_image)
hide_button = ttk.Button(mainframe, text="Hide", command= lambda x=test_image_label:
                  layout.hide_image(x))
test_text_label = ttk.Label(mainframe, text="here i am")
empty_label = ttk.Label(mainframe, text="")

for child in mainframe.winfo_children():
    child.grid_configure(padx=5, pady=5)

entry_label.grid(column=0, row=0)
image_path_entry.grid(column=1, row=0)
hide_button.grid(column=0, row=3)
select_button.grid(column=0, row=4)
test_image_label.grid(column=0, row=5)
empty_label.grid(column=0, row=6)


image_path_entry.insert(0,TEST_PHOTO_PATH)
image_path_entry.focus()
breakpoint()



root.mainloop()

I have created this app for javascript beginners. Users can attempt daily quiz and see the explanation after each answer. Also providing the frequently used code snippets, you can download beautiful images of code snippets and quiz. Please provide your feedback.

Does anyone else find javascript/electron-based code editors confusing? I can never understand the organization/hierarchies of menus, buttons, windows, tabs. All my time is spent hunting through the interface. My kingdom for a normal dialogue box!

I've tried and failed to use VSCodium on a bunch of occasions for this reason. And a couple other ones. It's like the UI got left in the InstaPot waaaay too long and now it's just a soggy stewy mess.

Today I finally thought I'd take the first step toward android development. Completing a very simple hello world tutorial is proving to be challenging just because the window I see doesn't precisely correspond to the screenshots. Trying to find the buttons/menus/tools is very slow as I am constantly getting lost. I only ever have this in applications with javascript-based UIs

Questions:

1. Am I the only one who faces this challenge?

2. Do I have to use Android Studio or it there some kind of native linux alternative?

edited to reflect correction that Android Studio is not electron

Hi, I'm looking to open-source a small CLI application I wrote and I'm struggling with how to provide the built app since just providing the binary will not work. I had a friend test it and he had to compile from source due to glibc version differences.

My first thought was providing it as a flatpak but that isn't really suitable for CLI software.

I've googled around a bit and most guides I find just mention packaging separately for multiple package managers/formats (rpm, apt etc.). This seems really inefficient/hard to maintain. What is the industry standard for packaging a Linux software for multi-distro use?

Hi everyone,

TL;DR Completely new to coding and programming, but I want to learn enough to be able to run a home server, my own website and tinker a bit with Arduino. Is there any programming language or path that you could recommend?

I don't know if those things are related or not. I've been looking at books a bout Arduino, but it's just following instructions to do xyz, but not explanation of the basics.

About the server and website, I've wanted to try it out since I stumbled upon the Low tech magazine. Many of the projects there and the philosophy behind it speak to me, so I would like to be more knowledgeable about it and be able to do some stuff myself.

EDIT. You guys are awesome! Thank you so much for the replies. It’s so cool to see Lemmy populated with cool people willing to chat and put knowledge in common :) I might be updating this post when I get to do something about… well all the resources you gave me!

cross-posted from: https://lemmy.ml/post/13353225

Quick little confusion or even foot-gun I ran into (while working on the challenge I posed earlier).

TLDR

My understanding of what I ran into here:

• Matching on multiple variables simultaneously requires assigning them to a tuple (?),
• which happens more or less implicitly (?),
• and which takes ownership of said variables.
• This ownership doesn't occur when matching against a single variable (?)
• Depending on the variables and what's happening in the match arms this difference can be the difference between compiling and not.

Anyone got insights they're willing to share??

Intro

I had some logic that entailed matching on two variables. Instead of having two match statements, one nested in the other, I figured it'd be more elegant to match on both simultaneously.

An inline tuple seemed the obvious way to do so and it works, but it seems that the tuple creates some ownership problems I didn't anticipate, mostly because I was thinking of it as essentially syntax and not an actual tuple variable.

As you'll see below, the same logic with nested match statements each on a single variable doesn't suffer from the same issues.

Demo Code

fn main() {

    // # Data structures
    enum Kind {
        A,
        B
    }
    struct Data {
        kind: Kind
    }

    // # Implementation
    let data = vec![Data{kind: Kind::A}];

    // ## Basic idea: process two adjacent data points
    let prev_data = data.last().unwrap();
    let new_data = Data{kind: Kind::B};

    //

MATCH STATEMENTS

// ## This works: match on one then the other
let next_data = match prev_data.kind {
    Kind::A => match new_data.kind {
        Kind::A => 1,
        Kind::B => 2,
    },
    Kind::B => match new_data.kind {
        Kind::A => 3,
        Kind::B => 4,
    },
};

// ## This does NOT work: match on both
let next_data2 = match (prev_data.kind, new_data.kind) {
    (Kind::A, Kind::A) => 1,
    (Kind::A, Kind::B) => 2,
    (Kind::B, Kind::A) => 3,
    (Kind::B, Kind::B) => 4,
};

}

### The Error

The error is on the line `let next_data = match (prev_data.kind, new_data.kind)`, specifically the tuple and its first element `prev_data.kind`, with the error:

error[E0507]: cannot move out of prev_data.kind which is behind a shared reference

move occurs because prev_data.kind has type Kind, which does not implement the Copy trait

### The Confusion

So `prev_data.kind` needs to be moved.  That's ok.  Borrowing it with `(&prev_data.kind, ...)` fixes the problem just fine, though that can cause issues if I then want to move the variable within the match statement, which was generally the idea of the logic I was trying to write.

What got me was that the same logic but with nested match statements works just fine.

I'm still not clear on this, but it seems that the inline tuple in the second tuple-based approach is a variable that takes ownership of the variables assigned to it.  Which makes perfect sense ... my simple mind just thought of it as syntax for interleaving multiple match statements I suppose. In the case of nested match statements however, I'm guessing that each match statement is its own scope.

**The main thing I haven't been able to clarify is what are the ownership dynamics/behaviours of match statements??**  It seems that there's maybe a bit happening implicitly here??  I haven't looked super hard but it does seem like something that's readily glossed over in the materials I've seen thus far??

### General Implications

AFAICT:
* if you want to match on two or more variables simultaneously, you'll probably need borrow them in the match statement if they're anything but directly owned variables.
* If you want to then use or move them in the match arms you may have to wrangle with ownership or just use nested match statements instead (or refactor your logic/implementation).
* **So probably don't do multi-variable matching unless the tuple of variables is a variable native to the logic**?