设置/访问由map< string，boost :: any>创建的锯齿地图值。 [英] set/access jagged map values made with map<string, boost::any>

问题描述

我已显示如何创建锯齿状的多维 std :: map 使用 boost :: any 。

但是，例如此答案。

当我使用

  accounts [bank] [cash] = 100; 
  
 
 
 
  gcc  
 
 
 错误：accounts.std :: map <_Key，_Tp，_Compare，
 _Alloc> ; :: operator []< std :: basic_string< char>，boost :: any，
 std :: less< std :: basic_string< char> >，std :: allocator< std :: pair< const 
 std :: basic_string< char>，boost :: any> > >（（*& std :: basic_string< char>（（const 
 char *）bank），（*（const std :: allocator< char> *）（& std :: allocator< ; char>（））））））[cash]'
  
 
 
如何使用锯齿状的多维 map 使用 boost :: any 创建？ （
 
 
 
 多维声明
 strong> 
  std :: map< std :: string，boost :: any>帐户; 
 accounts [bank] = std :: map< std :: string，boost :: any>（）; 
 accounts [bank] [cash] = 100; 
  
   json-spirit   
 
 
 
并尝试使用json-spirit的 mObject ，因为所有这些似乎已经内置了。
 
 
 
有趣的是使用完全相同的符号，我得到完全相同的错误。 
解决方案
 
  std :: map< std :: string，boost :: any>帐户; 
 accounts [bank] = std :: map< std :: string，boost :: any>（）; 
 accounts [bank] [cash] = 100; 
  
当然这会导致编译时错误，你放在boost :: any std :: map，
但编译器不知道这个。 account [bank]有boost :: any类型，
和boost :: any没有
  int&阅读boost :: any的工作原理： http://www.boost.org/doc/libs/1_54_0/doc/html/any/s02.htmlrel =nofollow> http://www.boost.org/doc/libs/1_54_0/doc/ html / any / s02.html  
 
 
 
修正是微不足道的：
  #include< boost / any.hpp> 
 #include< map> 
 #include< string> 
 
 int main（）
 {
 std :: map< std :: string，boost :: any>帐户; 
 accounts [cash] = 100; 
 accounts [bank] = std :: map< std :: string，boost :: any>（）; 
 boost :: any_cast< std :: map< std :: string，boost :: any> &>（accounts [bank]）[cash] = 100; 
} 
  
 
I've been shown how to create a jagged multidimensional std::map by using boost::any.

However, I'm having trouble setting the values like in this answer.

When I use
accounts["bank"]["cash"] = 100;
gcc gives this error
error: no match for ‘operator[]’ in ‘accounts.std::map<_Key, _Tp, _Compare, 
_Alloc>::operator[]<std::basic_string<char>, boost::any, 
std::less<std::basic_string<char> >, std::allocator<std::pair<const 
std::basic_string<char>, boost::any> > >((* & std::basic_string<char>(((const 
char*)"bank"), (*(const std::allocator<char>*)(& std::allocator<char>())))))["cash"]’
How can a jagged multidimensional map created with boost::any be accessed?  (If there is a better technique to do this, please show me.  I only care about what works and is quick to write.)

multidimensional declaration
std::map<std::string, boost::any> accounts;
accounts["bank"] = std::map<std::string, boost::any>();
accounts["bank"]["cash"] = 100;
json-spirit

I gave up and tried to use json-spirit's mObject instead since all of this seems already built in.

Funny thing is is that with the exact same notation, I get the exact same error. 
解决方案
std::map<std::string, boost::any> accounts;
accounts["bank"] = std::map<std::string, boost::any>();
accounts["bank"]["cash"] = 100;
Of course this cause compile time error, you put to boost::any std::map,
but compiler have no idea about this. accounts["bank"] has "boost::any" type,
and boost::any have no 
int& operator[](const char *)
Read how boost::any works: http://www.boost.org/doc/libs/1_54_0/doc/html/any/s02.html

Fix is trivial:
#include <boost/any.hpp>
#include <map>
#include <string>

int main()
{
  std::map<std::string, boost::any> accounts;
  accounts["cash"] = 100;
  accounts["bank"] = std::map<std::string, boost::any>();
  boost::any_cast<std::map<std::string, boost::any> &>(accounts["bank"])["cash"] = 100;
}


                        
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