problem reading json string with minijson-reader library - c++

Question

While trying parsing a json string in my c++ code, using the library minijson, I got a code like that so far:
<<"version">> [&]() { result.setVersion(v.as_long()); }
<<"capabilities">> [&]()
{
parse_array(ctx, [&](value capability)
{
result.getCapabilities().push_back(capability.as_string());
});
}
the data should be stored on this struct:
struct block_template {
int version;
vector<string> capabilities;
...
}
the version value is stored correctly, but the vector is staying with size 0. I try visualize the data being read from the json string ( with cout << capability.as_string() << endl ) and it's display correctly, just not being stored in the data structure.
Anyone who already worked with this library can give a hint of what's wrong here?

Answer 1

Since the OP asks for examples using other libraries in the comments, I'll reply more generally.
In jsoncons, if the JSON member names and the C++ variable names were the same, you could use the macro JSONCONS_ALL_MEMBER_TRAITS to set up the mappings,
#include <iostream>
#include <jsoncons/json.hpp>
struct block_template {
int version;
std::vector<std::string> capabilities;
};
JSONCONS_ALL_MEMBER_TRAITS(block_template, version, capabilities)
int main()
{
std::string input = R"(
{
"version" : 1,
"capabilities" : ["foo","bar","baz"]
}
)";
auto result = jsoncons::decode_json<block_template>(input);
std::cout << "(1)\n" << "version: " << val.version << "\n";
for (auto& item : val.capabilities)
{
std::cout << "item: " << item << "\n";
}
std::string output;
jsoncons::encode_json(val, output, jsoncons::indenting::indent);
std::cout << "(2)\n" << output << "\n\n";
}
Output:
(1)
version: 1
item: foo
item: bar
item: baz
(2)
{
"capabilities": ["foo", "bar", "baz"],
"version": 1
}
And if the JSON and C++ names were different, you could use the macro JSONCONS_ALL_MEMBER_NAME_TRAITS instead,
JSONCONS_ALL_MEMBER_NAME_TRAITS(block_template, (version,"Version"),
(capabilities,"Capabilities"))
With this change, the output becomes:
(1)
version: 1
item: foo
item: bar
item: baz
(2)
{
"Capabilities": ["foo", "bar", "baz"],
"Version": 1
}
See this answer for more examples of libraries that decode JSON to C++ data structures and encode back again, including Martin York's interesting ThorsSerializer.