adding std::map to init list of ctor

Question

I want to add a std::map m_mapName in the initialization list of the constructor.

If I type m_mapName() in the constructor's init list, the compiler accepts it.

But, is it correct? If it is not correct, how can I add the map to the initialization list?

Then, I do several insertions in the map. What is a more elegant way of inserting values, so I don't call insert function everytime?

More info:

Just like in : C++, can I statically initialize a std::map at compile time?, the compiler doesn't accept syntax like:

std::map<int, char> example = { (1,'a'),
                            (2, 'b'),
                            (3, 'c') };

Cannot use Boost. My code looks like this:

* className.h: *

typedef std::map <uint16_t, int> mapType;

typedef std::pair <uint16_t, int> mapPair;

className{

private: 

    mapType m_mapName; 

}

* className.cpp: *

className::className () : 

m_mapName()

{

...

m_mapName.insert(mapPair(someMapValue1, 0));

m_mapName.insert(mapPair(someMapValue2, 0));

m_mapName.insert(mapPair(someMapValue3, 0));

Did you read the answers on the question you linked to that say exactly how to do this? — Mooing Duck
– Mooing Duck, Commented Dec 13, 2014 at 0:58
Yes, I did. The posting doesn't answer my specific question: Why did the compiler accept the way I added the map to the init list and if it is correct? — Developer
– Developer, Commented Dec 13, 2014 at 1:13
That's not what your code looks like, you're missing class and a semicolon at least. stackoverflow.com/help/mcve — Mooing Duck
– Mooing Duck, Commented Dec 14, 2014 at 18:55

Mooing Duck · Accepted Answer · 2014-12-13 01:18:00Z

0

Yes, your code is correct. And the linked question shows what to initialize it with

className::className () 
:m_mapName{ 
    {someMapValue1, 0}, 
    {someMapValue2, 0}, 
    {someMapValue3, 0}}
{}

answered Dec 13, 2014 at 1:18

Mooing Duck

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4 Comments

Developer Over a year ago

The approach above gives me: no matching function for call to 'std::map<short unsigned int, int, std::less<short unsigned int>, std::allocator<std::pair<const short unsigned int, int> > >::map(<brace-enclosed initializer list>)'

Developer Over a year ago

Changed the type from 'uint16_t' to 'int'. The code looks like: className::className () :m_mapName{ {0, 0}} {} Unfortunately, I get expected '{' before 'm_mapName' and expected constructor, destructor, or type conversion before '{' token

Developer Over a year ago

I guess my code the way it is works because somehow m_mapName() calls some default constructor. But I am not sure

Mooing Duck Over a year ago

Also, I can't reproduce your issue: coliru.stacked-crooked.com/a/2cccca1a328c81c7

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