How to wrap a class derived from vector in swig

Question

I want to wrap a class derived from std::vector with some extend functions into csharp with swig. the functions from vector are also needed like push_back to add new item into the class (which named Add in csharp).

I tried with default setting with swig, IntArray is valid in csharp .But, vector's functions are invalid.

if i try to define a vector in the .i file:

namespace std{
%template(ScalarVec) vector<ScalarTest>; 
}

a class named ScalarVec have functions like vector is valid in csharp, but without the extend function.

How to wrap the ScalarArray to csharp with swig?

The following is a simple example.

#include <vector>
#include <numeric>
namespace test
{
    struct ScalarTest {
        int val;
    };
    struct ScalarArray : public std::vector<ScalarTest>
    {
        int sum() const { 
            int res = 0;
            for (const ScalarTest &item : *this) {
                res += item.val;
            }
            return res;
        }
    };
}

Answer 1

SWIG is picky about order of declarations. Below correctly wraps your example code and can call the sum function. I'm not set up for C# so the demo is created for Python:

test.i

%module test

%{
// Code to wrap
#include <vector>
#include <numeric>

namespace test
{
    struct ScalarTest {
        int val;
    };
    struct ScalarArray : public std::vector<ScalarTest>
    {
        int sum() const { 
            int res = 0;
            for (const ScalarTest &item : *this) {
                res += item.val;
            }
            return res;
        }
    };
}
%}

namespace test
{
    struct ScalarTest {
        int val;
    };
}

%include <std_vector.i>
// Must declare ScalarTest above before instantiating template here
%template(ScalarVec) std::vector<test::ScalarTest>;

// Now declare the interface for SWIG to wrap
namespace test
{
    struct ScalarArray : public std::vector<ScalarTest>
    {
        int sum() const;
    };
}

demo.py

import test
x = test.ScalarArray()
a = test.ScalarTest()
a.val = 1
b = test.ScalarTest()
b.val = 2
x.push_back(a)
x.push_back(b)
print('sum',x.sum())
print(x[0].val,x[1].val)

Output:

sum 3
1 2