Fail to use function template with array as parameter inside a class

Question

I created a function template. It works fine if I use it in functions. Now, I'd like to use it inside a class but can't make the code compile:

#include <QList>

// Function template
template <typename T>
void Array2QList(QList<T> &outList, const T in[], int &insize)
{
    for (int i = 0; i < insize; ++i)
        outList.append(in[i]);
}

// Class using the template    
class Parser
{
public:
    Parser(const unsigned char buffer[], const int numBytes){
        Array2QList<>(frame, buffer, numBytes); // This one fails
    }
    ~Parser(){}
    QList<unsigned char> frame;
};

// Main
int main(int argc, char *argv[])
{
    int size = 50;
    unsigned char buffer[size];

    QList<unsigned char> frame;

    Array2QList<unsigned char>(frame, buffer, size); // This one works

    Parser parser = Parser(buffer, size);
    return 0;
}

The error I get is:

..\SandBox\main.cpp: In constructor 'Parser::Parser(const unsigned char*, int)':

..\SandBox\main.cpp:20: error: no matching function for call to 'Array2QList(QList&, const unsigned char*&, const int&)'

Note: I must arrays since it is an interface for a USB driver.

TartanLlama · Accepted Answer · 2015-05-12 10:47:47Z

2

Array2QList<>(frame, buffer, numBytes);

Here, numBytes is a const int, but Array2QList takes an int&. You can't bind a non-const reference to something that's const. It's unclear why you are taking that parameter by reference, so if you just pass by value instead, it'll work.

template <typename T>
void Array2QList(QList<T> &outList, const T in[], int insize){
//                                     get rid of &  ^

answered May 12, 2015 at 10:47

TartanLlama

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1 Comment

Plouff Over a year ago

Thank you! It was indeed the const. I got confused since I have 2 functions with the same name but not the same parameters. The other one uses a reference to the size because the array is allocated inside the function. In the case I don't need the reference... But I wrongly kept it.

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