Encoding in the QTableView

mrjj

@ro12man3
hi
Starting with models and view are not best intro to Qt.
They are very powerful but does demand some c++ skills and reading the docs.

Sometimes code is easier to understand so I made u sample with @SGaist help.

It has a list of names and if it sees Lars, it replaced it with BANNED.
For your code, you will use the hash to look up the name from the code.

https://www.dropbox.com/s/vsiqjrr41jhafqo/myfirstview.zip?dl=0

the key points to understand is:
we make a new class to override the default behaviour

class MyDelegate : public QStyledItemDelegate {
public:
MyDelegate(QObject* parent)
: QStyledItemDelegate(parent) {}
virtual QString displayText(const QVariant& value, const QLocale& locale) const;
};

We set this delegate ONLY to the column we need.

ui->tableView->setItemDelegateForColumn(0, new MyDelegate(this));

the displayText is the key function.:

QString MyDelegate::displayText(const QVariant& value, const QLocale& locale) const {
if (value.toString().compare("Lars") == 0) // if found
return "BANNED";
else
return value.toString(); // else just return data unchanged
}

Here u will replace the city-code with names using the hash.

Hope this helps you.

ro12man3

@mrjj ohhh thank you! It works!! Thank you very much.

But I have 40 values that I will need to change(if it will be in quiery result).

I can't write 40 "else if".. "else if"... "else if".... That's unlogic.
I need to write all that values in support *.txt file(or another, the main is a simple format for editing), cause if I will write all that values in the program and then I will need to add new values...That's will be very uncomfortable.

I see the method of the working the function so:
The function is searching the values(from *.txt file) that has a quiery result. If it will find, then it will change to another every value.

But...how make that in reality?

mrjj

hi
it sounds like your best way would to read in
the text file to a hash.
and use that hash in displayText
I agree, using if for 40 values would be nasty :)

How does your text file look like?

ro12man3

@mrjj I didn't create that file, cause I have no idea. Well, every variant will be good. The main is the working code :D

Do you think that *.txt file should looks so:

hash.insert("123", "Jack Sparrow");
hash.insert("134", "Elvis Presley");
hash.insert("201", "Walter White");
........

?

mrjj

@ro12man3
Hi
For me it sounds like you would have a text file with
1000, NAME1
1001, NAME2

so when u see int 1000, u want "NAME" etc.

So your task is to look at QFile and read in a text file with your format and stuff it into a hash.
Then use it.

ro12man3

@mrjj ok, I understand how to read the file and search the values. I don't understand another thing.
On example=, the function will read the .txt file and it will find some value. Let it be 2900.
In txt file it will be looking:
2900, "Jackson"

How to convert to "Jackson"? I don't know how to write that in a hash. How the hash will look the "convert value"?

mrjj

@ro12man3
say
u define the hash like
QHash<int, QString> Hash;
it means we use int as key and get string as result
so
QString Name=hash[2900];
would give us "Jackson" in name;

please read doc on how it works.
http://doc.qt.io/qt-5/qhash.html

so you would read all lines from text file and insert into hash.

ro12man3

@mrjj woooow thank you! You are the master! :) I understand, very clever idea!

I will try that in the morning.

mrjj

well for 40 lookups its more fun that tons of ifs
if u make a text file with
ID, NAME
like
1000, TOWN
1001, TOWN2
1002, TOWN3

so u need to ( code handwritten fast, not tested. u need to add includes)

QFile file("c:/mynames.txt");
if(!file.open(QIODevice::ReadOnly)) {
QMessageBox::information(0, "error", file.errorString());
}

QTextStream in(&file);
while(!in.atEnd()) {
QString line = in.readLine(); // get a line from file
QStringList fields = line.split(","); <<< KEY point. we ask it to split the text at "," to a list
/// now fields[0] is first part and fields[1] is rest
// so
hash[fields[0].toInt()] = fields[1] ; // store name under key
}

file.close();

ro12man3

@mrjj thank you very much!! I will try that. If I wiil edit this, I will write here the correct code.
Thank you for your helping!

mrjj

@ro12man3
You are very welcome.
One note is that if u read in text lines then
it will be text so u need to convert to int for the key if you
define the hash like that.
QHash<int, QString> Hash;
something like
hash[ fields[0].toInt() ]=xxx
If it gives u grief , let me know as im not 100% sure of syntax as its free writing :)

ro12man3

@mrjj Well, I can extract the second field, but it will be all second fields.

And I have edited the code:

QString MyDelegate::displayText(const QVariant& value, const QLocale& locale) const {
       QString line;
        QFile file("C:/QT/Test text/1.txt");
        if(!file.open(QIODevice::ReadOnly))
               qDebug() << "Error opening file";
        QTextStream in(&file);

        QHash<int, QString> hash;

         while(!in.atEnd()) {
         QString line = in.readLine(); 
         QStringList fields = line.split(","); 
         hash[fields[0].toInt()] = fields[1] ; 
  if (value.toString().compare(fields[0]) == 0)
    return fields[1];
  else
    return value.toString(); 
}
}

And it doesn't work. How to solve that?
It was working when I wrote

 if (value.toString().compare("1000") == 0)
    return "Jackson";

If I write

QMessageBox::information(this, fields[0], fields[1] );

it is working, but it shows ALL values.

mrjj

@ro12man3 said:

And it doesn't work. How to solve that?

You really have to provide more info that that :)
if you insert qDebug() << "f1=" << fields[0] << "f2=" << fields[1];
does it read in the data correctly ? this is critical.
Also you build the hash
hash[fields[0].toInt()] = fields[1] ;
but don't use it. ? You dont use it to look up the text.
QString CityName = hash[value.toInt()];
return CityName;
Also you mix reading in the file with compare value. that is wrong.
You should not read it in displayText as it will then read file each time
it draw that column. that is not so good.
Make Hash a member of the class. (in .h) and just use it
in displayText. then u can read it once and use it over and over.
Read in the text file in the constructor of the delegate;

SGaist

In addition to what @mrjj wrote: make the hash a member of your delegate.

ro12man3

@mrjj said:

You really have to provide more info that that :)
if you insert qDebug() << "f1=" << fields[0] << "f2=" << fields[1];
does it read in the data correctly ? this is critical.

Yes, I can extract this values. I tested that in QMessageBox.
More info... http://rghost.ru/7wFZPWC4v This is the project.
Download link(http://rghost.ru/download/7wFZPWC4v/ccf2cf56d3bbd353e8db12f377907d858f261e23/ccf2cf56d3bbd353e8db12f377907d858f261e23/myfirstviewEDITED.rar)

It's not very difficult code structure, I don't know why it's not working.

SGaist

Hi,

Because it's not buildable as is.

MyDelegate::MyDelegate(QObject *parent)
    : QStyledItemDelegate(parent)
{
    QString line;
    QFile file("1.txt");
    if(file.open(QIODevice::ReadOnly)) {
        QTextStream in(&file);
        while(!in.atEnd()) {
            QString line = in.readLine(); // get a line from file
            QStringList fields = line.split(","); // KEY point. we ask it to split the text at "," to a list
            hash[fields[0].toInt()] = fields[1] ; // store name under key
        }
    } else {
        qDebug() << "Error opening file";
    }
}

// this is the key delegate function!
QString MyDelegate::displayText(const QVariant& value, const QLocale& locale) const {
     return hash.value(value.toInt());
}

[edit: code cleanup SGaist]

mrjj

oh a tad to late :)
https://www.dropbox.com/s/3ajogwsoc7n1zjg/myfirstviewEDITED_hash.zip?dl=0

SGaist

Note that the build problem isn't with the delegate but with the MainWindow missing slot implementation.

@mrjj :-D

ro12man3

@mrjj @SGaist oooohhh guys, thank you!! You are amazing!!!

It's working. !!!

The problem is SOLVED! THANK YOU VERY MUCH!!

ro12man3

@mrjj @SGaist
I started to work and I found one bag.
My table is:
Roberto
Jackson
1002
1
And that's my txt file:
1002,Hello
1,How are you
So the result in the table is
Roberto
Jackson
Hello
How are you

It's good. Correct work.
But if I change 1002 to 10--02 then all const values in the table will become like a second value for 10--02. The result will become:
Hello
Hello
Hello
How are you
You can see that, just edit in table Maria to 10--02 and add 10--02 to txt file. What is that?