Replies: 4 comments 5 replies
-
|
You do not need to write conversions for namespace nlohmann
{
template <typename T>
struct adl_serializer<std::shared_ptr<T>>
{
static void to_json(json& j, const std::shared_ptr<T>& opt)
{
if (opt)
{
j = *opt;
}
else
{
j = nullptr;
}
}
static void from_json(const json& j, std::shared_ptr<T>& opt)
{
if (j.is_null())
{
opt = nullptr;
}
else
{
opt.reset(new T(j.get<T>()));
}
}
};
}Complete example: #include <iostream>
#include "json.hpp"
using json = nlohmann::json;
namespace nlohmann
{
template <typename T>
struct adl_serializer<std::shared_ptr<T>>
{
static void to_json(json& j, const std::shared_ptr<T>& opt)
{
if (opt)
{
j = *opt;
}
else
{
j = nullptr;
}
}
static void from_json(const json& j, std::shared_ptr<T>& opt)
{
if (j.is_null())
{
opt = nullptr;
}
else
{
opt.reset(new T(j.get<T>()));
}
}
};
}
struct foo {
int i = 42;
};
void to_json(json& j, const foo& f)
{
j["i"] = f.i;
}
int main()
{
auto shared_foo = std::make_shared<foo>();
std::shared_ptr<foo> null_foo = nullptr;
json j_foo = shared_foo;
json j_null = null_foo;
std::cout << j_foo << '\n' << j_null << std::endl;
} |
Beta Was this translation helpful? Give feedback.
-
|
Thanks. Any reason why Also do you have a solution for the |
Beta Was this translation helpful? Give feedback.
-
|
Beta Was this translation helpful? Give feedback.
-
|
Does this also work with raw pointers? I am using a software architecture synthesis system that I wrote myself and that synthesizes C++ classes with inheritance and stl container member variables from a BNF like description. I am now adding json serialization and deserialization to it so that I can serialize and deserialize every generated class on the fly and that the serialisation code gets automatically updated when the BNF description changes. So yesterday I put the to_json part in, and then I got stuck on the raw pointers. These do not really work out of the box, but then I generated virtual to_json functions which also work with super classes like suggested over here, So this works, but then I got stuck again on the raw pointers in my stl containers. So of course I can generate some dereferencing code for that as well but is there a way to make raw pointers work directly? Or, like I am seeing here, should I wrap each raw pointer inside a std::shared_ptr and then use that? I could do that as well of course, and then there is probably no need for extra code to serialize containers with shared_ptrs? An other thing I need to solve are the multimaps because I want to serialize the whole equal range so I need to wrap those in separate arrays.... |
Beta Was this translation helpful? Give feedback.
-
|
Was this supposed to work only for pure Lots of errors but in the end: |
Beta Was this translation helpful? Give feedback.
-
|
Yes, should work: std::vector<std::shared_ptr<foo>> v;
v.emplace_back(std::make_shared<foo>());
v.emplace_back(nullptr);
std::cout << json(v) << std::endl;
Output: [{"i":42},null] |
Beta Was this translation helpful? Give feedback.
-
|
Hmmm got it. Looks like it works if I use this shared_ptr serializer you suggested. However, there's an specific case where I need to do and it's trying to use the I need to use Do you have any idea on what's happening? |
Beta Was this translation helpful? Give feedback.
-
|
Looks like Output, if helpful: |
Beta Was this translation helpful? Give feedback.
-
|
@LucasZanella could you elaborate more on how you were able to resolve your issue? I am facing a similar issue where |
Beta Was this translation helpful? Give feedback.
-
In order to parse
std::vector<std::shared_ptr<VPN>>where VPN can be the subtypes
OpenVPNand other types likeMicrosoftVPN,CiscoVPN, etc, I had to do the following:then, for each subtype, I implement the
to_jsonandfrom_json:As you can see, I got many problems, like
if (j.at("type") == "OPENVPN"). I have to compare with the string literal instead of the enum before I create the instance ofVPNwith the subtypeOpenVPNfor example. I had multiple tries after a lot of segfaults to realize what I was doing.Apparently
std::vector<CustomObject>works without me having to do anything except implementingfrom_jsonandto_jsonforCustomObject. But ifCustomObject = std::shared_ptr<OtherCustomObject>then I need to implementfrom_jsonandto_jsonforstd::shared_ptr<OtherCustomObject>.Shouldn't or couldn't the library handle
std::vector<std::shared_ptr<CustomObject>>on its own? Do anybody have a better solution?Beta Was this translation helpful? Give feedback.
All reactions