CODEWITHSUNDEEP
qtqvector
aarelovich
aarelovich

Reputation: 5556

Modifying a QVector of QVectors passed as a pointer

I have a variable in the argument of a function that is defined like this:

QVector< QVector<qreal> > *var;

In a certain point of the code I want to do this:

*var[i][j] = some_value.

However this does not compile because

error: no match for ‘operator*’ in ‘*(var + ((long unsigned int)(((long unsigned int)row) * 8ul)))->QVector::operator[] with T = QVector’

How do I properly reference the value so that it is modified? (The idea is that the parameter passed in the function is really modified.)

Upvotes: 2

Views: 2388

Answers (1)

sam-w
sam-w

Reputation: 7687

You need to put *var in parentheses:

(*var)[i][j] = some_value;

Though why are you using a pointer to a QVector? Since QVector is part of Qt's generic containers family, it uses implicit sharing. This means that if you pass-by-value instead, you'll only perform a shallow copy, which is to say that you'll effectively only be passing the thin book-keeping part of the data structure - a pointer to a larger block of data which exists elsewhere.

Upvotes: 4

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