I am not understanding why. " error: no match for 'operator=' (operand types are 'QVector<int>' and 'int') queue[rear++]=value; ^"

thippu

I was practicing FIFO queue using QVector<int>* but I'm facing assignment error.
In the enque() and line queue[rear++]=value.
I could not able to correct it, asking for help.
code :

#define OPTION_LIMIT 4

#include <QCoreApplication>
#include<QVector>
#include<iostream>
using namespace std;
QVector<int> *queue=new QVector<int>;
int size;
int rear=-1;
int front=-1;


void enque()
{
    if(rear>size-1)
    {
        display();
    }
    else
    {
        if(front<0)
        {
            front=rear=0;
        }
        int value;
        cout<<"enter the content "<<endl;
        cin>>value;
        queue[rear++]=value;
        display();
    }
}

mrjj

Hi
You have a pointer to the queue.
QVector<int> *queue=new QVector<int>; // points to it

so you have to say
(*queue)[rear++]=value;
which really is
queue->operator=value;

However, if you dont use pointer to queue
QVector<int> queue;
then
queue[rear++]=value; works.

Anyway, there is something else

on empty one will crash.

so make sure you have called append to add elements or use
http://doc.qt.io/qt-5/qvector.html#reserve
so make it a size to start with.
or change the logic to
//queue[rear++]=value;
queue .append(value);
rear++;

Also Qt does have
http://doc.qt.io/qt-5/qqueue.html

thippu

@mrjj

@mrjj said in I am not understanding why. " error: no match for 'operator=' (operand types are 'QVector<int>' and 'int') queue[rear++]=value; ^":

you have to say
(*queue)[rear++]=value;

Thank you, bro build is fine now and I will make sure the queue is filled with zeros