Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Memory access by address
Forum Updated to NodeBB v4.3 + New Features

Memory access by address

Scheduled Pinned Locked Moved General and Desktop
5 Posts 3 Posters 1.3k Views 1 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • M Offline
    M Offline
    mohmo
    wrote on last edited by
    #1

    hey bros;
    I have a program to access the variables by their addresses and this is my code:

    float f;
    int t;

    QHash <int,int*> hash;
    hash.insert(1,&t);
    hash.insert(2,(int*)&f);

    *hash.value(1)=34;
    qDebug()<<"t1="<<t1; //t1= 34

    *hash.value(2)=456.987;
    qDebug()<<"f="<<f; //f=7.94536e-43 !!!!!!

    why this code is not working? and how can i fix that?
    Actually the objective of this code is to indexing every variable with any type (int, float, structure, Boolean, .. ) by an integer number. Hashing is used to achieve this goal.
    Thanks a lot

    1 Reply Last reply
    0
    • M Offline
      M Offline
      mohmo
      wrote on last edited by
      #2

      If i use QVariant like below:

      @QHash <int,QVariant*> hash;
      @
      and i insert the same values into it, i encounter this error:

      : error: C2664: 'QHash<Key,T>::insert' : cannot convert parameter 2 from 'int *' to 'QVariant *const &'
      with
      [
      Key=int,
      T=QVariant *
      ]

      But if i use the previous code and retrieve the address as below:
      @_(float_)hash.value(2)=456.987;
      qDebug()<<“f=”<<f; //f=456.987@

      everything will be OK.

      1 Reply Last reply
      0
      • JeroentjehomeJ Offline
        JeroentjehomeJ Offline
        Jeroentjehome
        wrote on last edited by
        #3

        Hi,
        Better to not use pointers to your variables for this. A QVariant will use the same amount of memory space as the variable it will point to. So, the QHash should have an <int, QVariant> not the pointer. Then add the variable to the QVariant via a constructor or other variant function and you should be able to convert any variable into that QHash. Even mix them if needed.

        Greetz, Jeroen

        1 Reply Last reply
        0
        • M Offline
          M Offline
          mohmo
          wrote on last edited by
          #4

          hey Jeroentje@home
          thanks for your reply But could you please make an example of your plan?

          1 Reply Last reply
          0
          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #5

            Jeroentje@home meant that you should follow koahnig's example

            @
            QHash<int, QVariant> hash;
            float fInput= 1.2
            hash.insert(1, fInput);
            float myFloat = hash.value(1).toFloat();
            @

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

            1 Reply Last reply
            0

            • Login

            • Login or register to search.
            • First post
              Last post
            0
            • Categories
            • Recent
            • Tags
            • Popular
            • Users
            • Groups
            • Search
            • Get Qt Extensions
            • Unsolved