could not convert '(<expression error>)' from '<brace-enclosed initializer list>' to std::unique_ptr<int []>

Question

I have the latest gcc compiler. gcc (Ubuntu 6.2.0-3ubuntu11~14.04) 6.2.0

On code::blocks I've set the compiler to the GNU Compiler as default.

The error I'm getting is this

error: could not convert {<expression error>} from <brace-enclosed initializer list> to std::unique_ptr<int []>

The issue is in my header file at the bottom.

This was for a lab that I did in class and It worked fine last week I think - compiling the header file gives me my results but when i build from the arrayclass.cpp file it gives me this error.

Here is my implementation file ArrayClass.cpp:

#include "ArrayClass.h"

#include <memory>

using std::make_unique;

ArrayClass::ArrayClass(int capacity)
  : arrSize{capacity},
    arr{make_unique<int[]>(capacity)}
{
}

void ArrayClass::insert(int value)
{
    if (currentSize < arrSize) {
        arr[currentSize++] =  value;
    }
}

void ArrayClass::set(int i, int value)
{
    if (i >= 0 && i < currentSize) {
        arr[i] =  value;
    }
}

int ArrayClass::get(int i) const
{
    if (i >= 0 && i < currentSize) {
        return arr[i];
    }
    else {
        return 0;
    }
}

int ArrayClass::capacity() const
{
    return arrSize;
}

int ArrayClass::size() const
{
    return currentSize;
}

And here is my header file:

#ifndef ArrayClass_header
#define ArrayClass_header
#include <memory>

using std::unique_ptr;
using std::make_unique;

class ArrayClass
{
public:
    // Constructors and Destructors

    // Default constructor
    // POST: Created an ArrayClass object with an array of size def_size
    // Compiler default suffices (see variable initializations at end of header)
    ArrayClass() = default;

    // Constructor
    // PRE: capacity > 0
    // POST: Created an ArrayClass object with an array of size capacity
    // PARAM: capacity = size of the array to allocate
    ArrayClass(int capacity);

    // Destructor
    // POST: All dynamic memory associated with object de-allocated
  //  ~ArrayClass();

    // Set the value of the next free element
    // PRE: currentSize < arraySize
    // POST: Element at index currentSize set to value
    // PARAM: value = value to be set
    void insert(int value);

    // Return an element's value
    // PRE: 0 <= i < arraySize
    // POST: Returned the value at index i
    // PARAM: i = index of value to be returned
    int get(int i) const;

    // Set an element's value
    // PRE: 0 <= i < arraySize
    // POST: Element at index i set to value
    // PARAM: i = index of element to be changed
    //        value = value to be set
    void set(int i, int value);

    // POST: Return the currently allocated space
    int capacity() const;

    // POST: Return the number of elements
    int size() const;

    // The default capacity
    static constexpr int def_capacity {10};

private:
    int arrSize {def_capacity};
    int currentSize {0};
    unique_ptr<int[]> arr {make_unique<int[]>(capacity)};
};

#endif

Answer 1

I'm pretty sure the error is here:

unique_ptr<int[]> arr {make_unique<int[]>(capacity)};

capacity should be def_capacity instead, since as of now, you're using the name of a function but without the round parentheses, which makes the compiler stumble while parsing the {} initializer list.

Edit : Yes, it compiles fine with the fix. There are two errors, the first one being " invalid use of non-static member function int ArrayClass::capacity() const ". Then the initializer-list one follows, since the compiler can't parse the initalizer list.

Edit 2 : In the .cpp file, in the constructor definition, capacity appears to shadow the ArrayClass::capacity() function, but I still think it'd be better to avoid such a collision just for clarity sake.