Call non-default constructor for object in vector initialization

Question

I want to initialize a vector in an initialization list of a constructor. The vector consists of objects with a parameterized constructor. What I have is:

Class::Class() : 
   raster_(std::vector< std::vector<Cell> > (60, std::vector<Cell>(80)))
{
...

How can I call Cell::Cell with two parameters in the above line? The obvious:

raster_(std::vector< std::vector<Cell(true,true)> > (60, std::vector<Cell(true,true)>(80)))

didn't work.

Thoroughly confused. Post the declarations for Class and Cell — John Dibling
– John Dibling, Commented Nov 24, 2010 at 13:40

icecrime · Accepted Answer · 2010-11-24 13:48:14Z

3

You should try :

Class::Class() : 
     raster_(60, std::vector<Cell>(80, Cell(true, true)))
{
    /* ... */
}

Note that I removed the useless std::vector<std::vector<Cell> > from the initializer. Also be aware that this could be highly ineffective depending on the cost of copying a Cell :

It creates an std::vector<Cell> by copying 80 times the provided value Cell(true, true)
It creates an std::vector<std::vector<Cell> > by copying 60 times the provided vector (which contains 80 elements itself) !

edited Nov 24, 2010 at 13:48

answered Nov 24, 2010 at 13:34

icecrime

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2 Comments

problemofficer Over a year ago

Oh, I didn't know I could ommit the type. You say its highly ineffective. How am I supposed to initialize the array then?

icecrime Over a year ago

@problemofficer: I guess it's fine as long as Cell is cheap to copy

Armen Tsirunyan · Accepted Answer · 2010-11-24 13:34:14Z

1

:raster_(std::vector< std::vector<Cell> > (60, std::vector<Cell>(80, Cell(true, true))));

if raster_ is something that takes the vector. If raster_ itself is the vector then like this

:raster(60, std::vector<Cell>(80, Cell(true, true)))

answered Nov 24, 2010 at 13:34

Armen Tsirunyan

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