Initializing a static std::map<int, STRUCTURE> in C++

Question

This post taught me how to initialize static std::map.

I could use this method to initialize a static map from int to STRUCTURE.

The code is as follows

#include <string>
#include <map>
#include <iostream>

typedef unsigned long GUID;

enum Function {
  ADDER = 1,
  SUBTRACTOR = 2,
  MULTIPLIER = 3,
  SQUAREROOT = 4
};

struct PluginInfo
{
    GUID guid;
    std::string name;
    Function function;

    PluginInfo(GUID guid, std::string name, Function function) : guid(guid), name(name), function(function) {}
    PluginInfo() {}
};

typedef std::map<GUID, PluginInfo> PluginDB;

PluginInfo temp1(1, "Adder", ADDER);
PluginInfo temp2(2, "Multiplier", MULTIPLIER);

PluginDB::value_type pluginDbArray[] = {
    PluginDB::value_type(1, temp1),
    PluginDB::value_type(2, temp2)
};

const int numElems = sizeof pluginDbArray / sizeof pluginDbArray[0];
PluginDB pluginDB(pluginDbArray, pluginDbArray + numElems);

int main()
{
    std::cout << pluginDB[1].name << std::endl;
}

Can I simplify the initialization code?

PluginDB::value_type pluginDbArray[] = {
    PluginDB::value_type(1, temp1),
    PluginDB::value_type(2, temp2)
};

I tried

PluginDB::value_type pluginDbArray[] = {
    PluginDB::value_type(1, {1, "Adder", ADDER}),
    PluginDB::value_type(2, {2, "Multiplier", MULIPILER})
};

However, I got error messages

mockup_api.cpp:24: error: expected primary-expression before ‘(’ token
mockup_api.cpp:24: error: expected primary-expression before ‘{’ token

I guess I can make the structure to contain only the data if this is possible.

struct PluginInfo
{
    GUID guid;
    std::string name;
    Function function;
}

Mark B · Accepted Answer · 2011-04-18 21:07:19Z

4

You can't do that in C++98/03. You may be able to do it with compound initializers in C++0x.

I think you can do this which may be good enough in C++98 though:

PluginDB::value_type pluginDbArray[] = {
    PluginDB::value_type(1, PluginInfo(1, "Adder", ADDER)),
    PluginDB::value_type(2, PluginInfo(2, "Multiplier", MULTIPLIER))
};

answered Apr 18, 2011 at 21:07

Mark B

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Robᵩ · Accepted Answer · 2011-04-18 21:23:00Z

1

I'd use Boost.Assignment :

#include <boost/assign/list_of.hpp>
...
/* no more temp1, temp2, or PluginDbArray */
...
PluginDB pluginDB = boost::assign::map_list_of
    (1, PluginInfo(1, "Adder", ADDER))
    (2, PluginInfo(2, "Multiplier", MULTIPLIER));

answered Apr 18, 2011 at 21:23

Robᵩ

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