QVector has no assign method?

[JonB]

@Publicnamer said in QVector has no assign method?:

Isn't there an automatically resized array?

As @jsulm says.
However if you really want this then (presumably, untested) you can derive from QVector and override the [] operator?

EDIT
I don't think you can override the [] operator after all?
In which case it may not be as "elegant" as you might wish, but you do realize that before going [index] you can insert

if (index >= qVector.size())
    qVector.resize(index);

Up to you whether you want to do this where you are using qVector[index] only as an l-value or also as an r-value (i.e. when writing to it versus reading from it, if I am using the wrong terminology).

[jsulm]

@JonB said in QVector has no assign method?:

I don't think you can override the [] operator after all?

Why not?

[Publicnamer]

@JonB said in QVector has no assign method?:

if (index >= qVector.size())
qVector.resize(index);

Yes that's what I'm doing now. It's a tiny inconvenience.

[Publicnamer]

@jsulm said in QVector has no assign method?:

Such a thing would be extremely dangerous

Not necessarily. It depends on the use case.

[Christian Ehrlicher]

@Publicnamer said in QVector has no assign method?:

Not necessarily. It depends on the use case.

Your example above will result in an oom exception after a few milliseconds. If you don't call this dangerous...

[JonB]

@jsulm said in QVector has no assign method?:

I don't think you can override the [] operator after all?

Because operator[] is listed among Public functions but does not say virtual?

[VRonin]

@JonB said in QVector has no assign method?:

Because operator[] is listed among Public functions but does not say virtual?

unlikely you need operator[] to be virtual. You normally don't use base classes interfaces for containers.

#include<QVector>
template <class T>
class ExpandingVector : public QVector<T>{
public:
    using QVector<T>::QVector;
    T& operator[](int index) {
        if (index >= QVector<T>::size())
            QVector<T>::resize(index+1);
        return QVector<T>::operator[](index);
    }
};

P.S.

There are many cases where

I still think there is no case where this is useful but you do you bro.

[JonB]

@VRonin
This is very useful, but I don't understand :)
If I use your template, but the base opertaor[] isn't virtual/overridable, what happens when some other code receiving my array as QVector<> parameter, not ExpandingVector<>, and then accesses it via []? They won't get my oevrride if it wasn't virtual?

[VRonin]

@JonB That's correct but 3rd party code receiving a QVector<> would need to stick to the QVector contract (i.e. index must be within bounds). ExpandingVector will behave exactly like QVector in that case.

[JonB]

@VRonin
Then I understand completely, thank you.

You just have your own definition of operator[]. You might as well have defined it as a foobar() method :)

[JKSH]

@Publicnamer said in QVector has no assign method?:

And yet a hash isn't good enough.

Why? Can you describe your use-case?

[JonB]

@JKSH I asked this too at the start, but no response....