NSMutableArray of NSNumber is nil after adding parsed float - opencv3.0

Question

I am trying to parse an array of Vectors (from C++'s std::vector) to an NSMutableArray of NSNumber. However, the Vector that I add to the NSNumber array is always nil, even after adding a NSNumber (parsed from std::vector)
In this project, I'm trying to connect the OpenCV Canny Edge Detection Algorithm (C++) to my Swift project. One of their methods returns all the photo's edges as std::vector. So, I'm trying to parse this into an array that is compatible with Swift (using Objective-C++ as the intermediary language). As of right now, it seems that only one line isn't working correctly (as stated above).
I am also a beginner Objective-C++ programmer, so there may be some common errors in the code, which I haven't found.
/*Ptr<LineSegmentDetector>*/
cv::Ptr<cv::LineSegmentDetector> ls = cv::createLineSegmentDetector(cv::LSD_REFINE_STD) ;//Creates the line detector (AKA what I called the edge detector)
std::vector<cv::Vec4f> lines_std;
[image convertToMat: &mat];
// Detect the lines
ls->detect(mat, lines_std);
//Swift compatible NSMutableArray to return from this method
NSMutableArray *edgeLines;
printf("currently finding the edge lines");
for (int i = 0; i < lines_std.size(); i ++) {
NSMutableArray<NSNumber *> *vector;
//Convert from Vec4f to NSNumber
for (int k = 0; k < 4; k ++) {
[vector addObject: [NSNumber numberWithFloat: (lines_std[i][k])]]; //HERE, I'm parsing each float value in each vector (from std::vector<cv::Vec4f>) and adding it to a NSArray, like a vector
}
//Here, I add the vectors to the return NSMutable array
[edgeLines insertObject:vector atIndex:edgeLines.count];
}
return edgeLines;
As stated above, the "vector" variable is always nil, even though I'm adding an NSNumber object to it.

Answer 1

I found the problem, I hadn't used this line:
NSMutableArray *vector = [[NSMutableArray alloc] init];