Vector values overwritten by last value in a loop

Question

I have the vector to store pointers of point clouds:

std::vector<pcl::PointCloud<PointType>::Ptr> List;

In a loop I am trying to push_back point cloud pointers in it.

pcl::PointCloud<pcl::PointXYZ>::Ptr  cloud(new pcl::PointCloud<pcl::PointXYZ>);

while(condition)
{...    
    List.push_back(cloud);
cloud->clear();
}

It adds point clouds, but at each iteration all values stored in the vector previously are replaced by the newly added value.

So lets say the size of the last point cloud I added is 400 and I added 5 point clouds in the iteration.

After the loop, if I check the sizes of stored 5 clouds, the results will be 400 400 400 400 400

Does anyone have an idea how to fix it?

Thanks

*"...but at each iteration..."* I don't see a loop, so how can we identify the problem? — Cory Kramer, Apr 14 '15 at 14:52
It looks like you are reusing the same pointer over and over and change the pointed-to object in each iteration of the loop. — Ralf Schallenberg, Apr 14 '15 at 14:58

score 4 · Accepted Answer · answered Apr 14 '15 at 14:58

It looks very much like you only create one point cloud, and in every iteration of your loop, you modify the point cloud, add a(nother) pointer to it to the vector, and repeat.

In other words, all your vector entries point to the same cloud, so every modification is of course visible through all entries.

score 0 · Answer 2 · answered Apr 14 '15 at 15:00

0

Rather than re-using your cloud variable over and over, which is the source of your issue, I would cut out the middle man

while(condition)
{   ...    
    List.emplace_back(new pcl::PointCloud<pcl::PointXYZ>);
}

answered Apr 14 '15 at 15:00

Cory Kramer

114,268
16
167
218

Vector values overwritten by last value in a loop

2 Answers2