Compilation fail with sync_schema and inheritance #854
Comments
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try adding explicit type to auto storage = sqlite_orm::make_storage("test.db"
, sqlite_orm::make_table<Base>("entries"
, sqlite_orm::make_column("id", &A::id, sqlite_orm::autoincrement(), sqlite_orm::primary_key())
, sqlite_orm::make_column("name", &A::name)
, sqlite_orm::make_column("timestamp", &A::timestamp)
, sqlite_orm::unique(&A::name, &A::timestamp)
)); |
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Perfect. Thank you. |
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Follow up, with How would you achieve that? Or is it best to avoid inheritance with sqlite_orm? |
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try |
Thanks you for the suggestion but this leads to complete code for reference: struct Base {
std::string name;
int64_t timestamp;
int64_t value;
};
struct A : public Base {
int64_t id;
};
auto storage = sqlite_orm::make_storage("test.db"
, sqlite_orm::make_table<Base>("entries"
, sqlite_orm::make_column("id", &A::id, sqlite_orm::autoincrement(), sqlite_orm::primary_key())
, sqlite_orm::make_column("name", &A::name)
, sqlite_orm::make_column("timestamp", &A::timestamp)
, sqlite_orm::unique(&A::name, &A::timestamp)
));
for (const auto& res : storage.sync_schema()) {
(void)res;
// check sync results here..
}
A a;
storage.insert(a); |
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I need to think here. Probably the first advice was wrong. I'll answer soon |
Alright thank you For this use case where you might want to reuse existing classes and structs and for storing I got the following workaround now: As described earlier I have a Base class struct Base {
std::string name;
int64_t timestamp;
int64_t value;
};I want to store Base objects while adding an additional field, an auto-increment id, without The table should look like this: auto storage = sqlite_orm::make_storage("test.db"
, sqlite_orm::make_table("entries"
, sqlite_orm::make_column("id", &A::id, sqlite_orm::autoincrement(), sqlite_orm::primary_key())
, sqlite_orm::make_column("name", &A::name)
, sqlite_orm::make_column("timestamp", &A::timestamp)
, sqlite_orm::unique(&A::name, &A::timestamp)
));With the following you will run into all kinds of problems: struct A : public Base {
int64_t id = -1;
};With an additional boilerplate and custom reference_value_wrapper it works: struct A : public Base {
int64_t id = -1;
db::ref_val_wrapper<std::string> name = Base::name;
db::ref_val_wrapper<int64_t> timestamp = Base::timestamp;
};The custom namespace db
{
template<typename T>
struct ref_val_wrapper
{
ref_val_wrapper(T& t) : refval(static_cast<T*>(&t)) {}
ref_val_wrapper(T&& t) : refval(std::move(t)) {}
inline ref_val_wrapper& operator=(T&& t)
{
if (std::holds_alternative<T*>(refval)) {
*std::get<T*>(refval) = std::move(t);
}
else {
std::get<T>(refval) = std::move(t);
}
return *this;
}
operator const T&() const
{
if (std::holds_alternative<T*>(refval))
return *std::get<T*>(refval);
else
return std::get<T>(refval);
}
[[nodiscard]]
inline const T& get() const
{
if (std::holds_alternative<T*>(refval))
return *std::get<T*>(refval);
else
return std::get<T>(refval);
}
[[nodiscard]]
inline T& get()
{
if (std::holds_alternative<T*>(refval))
return *std::get<T*>(refval);
else
return std::get<T>(refval);
}
[[nodiscard]]
inline bool is_value() const {
return std::holds_alternative<T>(refval);
}
[[nodiscard]]
inline bool is_reference() const {
return std::holds_alternative<T*>(refval);
}
private:
std::variant<T*, T> refval;
};
} // end namespace db
namespace sqlite_orm {
template<typename T>
struct type_printer<::db::ref_val_wrapper<T>> : public type_printer<T> {};
template<typename T>
struct statement_binder<::db::ref_val_wrapper<T>> {
int bind(sqlite3_stmt *stmt, int index, const ::db::ref_val_wrapper<T> &valueRef) {
return statement_binder<T>().bind(stmt, index, valueRef.get());
}
};
template<typename T>
struct row_extractor<::db::ref_val_wrapper<T>> : public row_extractor<T> {};
} // end namespace sqlite_orm |
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Nice thank you, hopefully I get time tonight to check it out. |
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👍 works for what I tested - inserting, iterating, iterating with where clauses. |
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@jahnf so you need to use |
Hey,
I think I found an Issue with inheritance and sync_schema:
With the following code, I get a compilation error:
Error output:
The text was updated successfully, but these errors were encountered: