CODEWITHSUNDEEP
c++stldictionarystruct
Hooked
Hooked

Reputation: 88238

Convert STL map into a struct

I have a std::map<string, double> whose members look something like:

X = [{"N", 200}, {"sigma", 1.0}, {"T", .2}]

Now, given the struct foo Y:

struct foo {
    int N;
    double T;
};

Can I programmatically map the key/value pairs X -> Y without writing a custom class for each X -> Y type mapping? Note that:

  1. X["sigma"] is not in Y, i.e. the mapping is not necessarily one-to-one
  2. The type of Y.N is an int while X["N"] is a double.

I suspect the answer is no, unless some trickery is done at compile time.

Edit: It may not be clear what I'm looking for. A pseudo-code version for this example would look something like:

if("N" in X) -> Y.N = X["N"];
if("T" in X) -> Y.T = X["T"];

Or programmatically:

for key in Y:
    if (key in X) -> Y.key = X[key]

Upvotes: 2

Views: 642

Answers (2)

Happy Green Kid Naps
Happy Green Kid Naps

Reputation: 1683

You want to set a field in an object of structure type based on the value of key in the map's elements (which is a string). So, no it cannot be done at compile time.

Upvotes: 0

MSalters
MSalters

Reputation: 180245

No. C++ has no concept of reflection. At compile time, there's no "foo::N" string anymore. The compiler has converted all occurances of foo::N in the source code to a 0 byte offset within Foo objects. Also, you cannot enumerate class members at compile time.

Upvotes: 4

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