Deserialize From SQLite Query

Unreal Engine bundles SQLite3 in SQLiteCore plugin and bundled with minimal C++ abstractions. In this example we implemented LoadStructArrayFromSQLite to load a SQLite query into a TArray of structs:

• DcSqlite.h
• DcSqlite.cpp

// DataConfigExtra/Public/DataConfig/Extra/Misc/DcSqlite.h
template<typename TStruct>
FDcResult LoadStructArrayFromSQLite(FSQLiteDatabase* Db, const TCHAR* Query, TArray<TStruct>& Arr)
// ...

With this method we can easily turn SQLite query results into structs that's easy to manipulate with:

// DataConfig/Source/DataConfigExtra/Private/DataConfig/Extra/Misc/DcSqlite.cpp
/// data fixture
FString Statement = TEXT("CREATE TABLE users (id INTEGER NOT NULL,name TEXT, title TEXT)");
bSuccess &= TestDb.Execute(*Statement);
Statement = TEXT("INSERT INTO users (id, name, title) VALUES (1, 'John', 'Manager')");
bSuccess &= TestDb.Execute(*Statement);
Statement = TEXT("INSERT INTO users (id, name, title) VALUES (2, 'Mark', 'Engineer')");
bSuccess &= TestDb.Execute(*Statement);
Statement = TEXT("INSERT INTO users (id, name, title) VALUES (3, 'Bob', 'Engineer')");
bSuccess &= TestDb.Execute(*Statement);
Statement = TEXT("INSERT INTO users (id, name, title) VALUES (4, 'Mike', 'QA')");

//  execute query and deserialize
TArray<FDcExtraTestUser> Arr;
UTEST_OK("Extra Sqlite", DcExtra::LoadStructArrayFromSQLite(
    &TestDb,
    TEXT("SELECT * FROM users WHERE title == 'Engineer' ORDER BY id"),
    Arr
    ));

//  equivalent fixture
FString Fixture = TEXT(R"(
    [
        {
            "Id" : 2,
            "Name" : "Mark",
            "Title" : "Engineer"
        },
        {
            "Id" : 3,
            "Name" : "Bob",
            "Title" : "Engineer"
        }
    ]
)");

For this to work we'll need to implement FSqliteReader which implements FDcReader API so it can be consumed by deserializer. The cool thing is that FSqliteReader works very well with SQLite's step API and can wrap SQLite error reporting into diagnostics that DataConfig can report.