better design pattern

Thank You

I want to know which type of design patter would you use and which would you think is best.

IG it will be quite long but instead of making many different questions, I will be doing in one.

Suppose, We will be using some database with some tables

I will try to simplify as much as I can
Let's Start

User_Email Table:

id	name	Email
1	Cute Mute	boi@email.com
3	Hes Mos	hey@email.com

User_post Table:

id	post
1	welcome
1	dope

Which approach would be best for connection of these data base and fetching all datas:
Taking these in consideration:

Design Pattern
Code Readability
Maintenance
Memory Footprint
Faster
Folder Structure

Let's suppose some scenario:

Name will be in drop-down menu in multiple widgets, lets say 10
User can post post and other data through different widgets. (Lets think that there are more than one 20 columns of data with separate insert , update and delete widget)

How to cope with this situation? I will mention my way, and I am very pleased to get it's bad sides.

Method 1:

creating widgets like updateusername.h , updatepost.h , createpost.h, updateemail.h and so on for all
And implementing them differently like:

Opening connection in main -> main.cpp or any other file that will execute at first
Getting connection and fetching same thing repeatedly over and over for multiple files.
Suppose, we want to fill all emails in QComboBox in all of files,
So creating fillEmail() in each file we have

Method 2:

creating widgets like mentioned in method one
Creating Database Controller class for every table
Like user_email.h

class userEmail{
public:
void updateEmail(int id, QString newEmail);
void updateName(int id, QString newName);
QVector<QString> getAllEmail();
QVector<QString> getAllName();
private:
int id;
QString name;
QString email;
};

and same for all tables and including that class in all file that we are gonna use this like
updateemail.h

#include"user_email.h"
// all class declaration-----
private:
userEmail thisOne;

// and in updateemail.cpp, use functions

If updatename.h is another file using this database, we include in same way and do rest of it.

Method 3:

Almost same as method 2,
but creating all database controllers as SINGLETONS, (may be less memory footprints? 🤔)

I can mostly think of these three patterns only.

I would be happy to get links and study materials if you feel I am not that mature with any of idea.

Ah!, It became quite long than expected.

SGaist

Hi,

Did you consider using QDataWidgetMapper ?

Thank You

@SGaist
Oh! Thank You, I will take a look on that.

It would be much nicer to get comments about my methods and my thinkings too 😁

SGaist

I would say a bit too complicated.

You seem to be ready to store a lot of data in each of your widgets rather than take advantage of the model view approach.

Thank You

@SGaist
Yes, I was waiting for something like this.
I am not really making application but want to know how to cope with something like this. It was in my mind for long time so I asked about it.
The last simple application I designed had these problem so I thought it would be much better to know about it before actually making another application

develop world

Yes I am also eager to know about this question 😀😀

SGaist

With a more detailed description about what your application will be about, it would be easier to discuss.

Thank You

@SGaist
Oh ! It's been long since last time I was in this forum.
You can think this application as application where users can fetch/post/export/update/delete data which are stored in different tables in database.
Suppose let's say about all "fetching" here (getting list of datas and filling in combobox, auto filling datas in update pages, showing datas in tableviews and things like these)

I had mentioned methods in the previous post. I would like to get your views on which method is efficient than others and consume less resources.
Is it good to load all data in constructor in every pages or create a controller and use that in different pages as needed?
Next one is If I have database mentioned above "user_email" Should I create a database page with functions like getName(QString email), getEmail(QString name), updateName(QString previousname), getAllDetails(QString name), deleteData(QString name), getTotalCount(), insertData(name,email)
or should I implement these on specific widgets as needed in that widget.

These fetched data could be used in different widgets and filled in combo boxes and other widgets as needed.

I had created one application. That used to fetch all data in constructor and it makes application load time nearly 30 seconds on some low end computers. So I feel like I should load data only when the widget is opened/shown. Which approach of data loading should be used?

SGaist

When data loading is slow, lazy loading is used so it only impacts on use.