Allow multiple types to be used as the key in fetch helpers

src/MediaLibrary.cpp

@@ -37,7 +37,7 @@ const std::vector<IFile*>& MediaLibrary::files()
     if ( m_files == NULL )
     {
         const char* req = "SELECT * FROM File";
-        SqliteTools::fetchAll<File>( m_dbConnection, req, 0, m_files );
+        SqliteTools::fetchAll<File>( m_dbConnection, req, m_files );
     }
     return *m_files;
 }

src/SqliteTools.h

 #ifndef SQLITETOOLS_H
 #define SQLITETOOLS_H
 
+#include <cstring>
 #include <sqlite3.h>
 #include <string>
 #include <vector>
 #include <iostream>
 
+template <typename T>
+struct TypeHelper
+{
+    static const T Default = {};
+};
+
+// Have a base case for integral type only
+// Use specialization to define other cases, and fail for the rest.
+template <typename T>
+struct Traits
+{
+    static constexpr
+    typename std::enable_if<std::is_integral<T>::value, int>::type
+    (*Bind)(sqlite3_stmt *, int, int) = &sqlite3_bind_int;
+};
+
+template <>
+struct Traits<std::string>
+{
+    static int Bind(sqlite3_stmt* stmt, int pos, const std::string& value )
+    {
+        char* tmp = strdup( value.c_str() );
+        sqlite3_bind_text( stmt, pos, tmp, -1, free );
+    }
+};
+
 class SqliteTools
 {
     public:
         static bool createTable(sqlite3* db, const char* request );
 
-        template <typename T, typename U>
-        static bool fetchAll( sqlite3* dbConnection, const char* req, unsigned int foreignKey, std::vector<U*>*& results)
+        template <typename T, typename U, typename KEYTYPE>
+        static bool fetchAll( sqlite3* dbConnection, const char* req, const KEYTYPE& foreignKey, std::vector<U*>*& results)
         {
             results = new std::vector<U*>;
             sqlite3_stmt* stmt;
@@ -23,8 +50,8 @@ class SqliteTools
                 std::cerr << sqlite3_errmsg( dbConnection ) << std::endl;
                 return false;
             }
-            if ( foreignKey != 0 )
-                sqlite3_bind_int( stmt, 1, foreignKey );
+            if ( foreignKey != TypeHelper<KEYTYPE>::Default )
+                Traits<KEYTYPE>::Bind( stmt, 1, foreignKey );
             res = sqlite3_step( stmt );
             while ( res == SQLITE_ROW )
             {
@@ -36,8 +63,14 @@ class SqliteTools
             return true;
         }
 
-        template <typename T>
-        static T* fetchOne( sqlite3* dbConnection, const char* req, unsigned int primaryKey )
+        template <typename T, typename U>
+        static bool fetchAll( sqlite3* dbConnection, const char* req, std::vector<U*>*& results)
+        {
+            return fetchAll<T, U>( dbConnection, req, 0, results );
+        }
+
+        template <typename T, typename KEYTYPE>
+        static T* fetchOne( sqlite3* dbConnection, const char* req, const KEYTYPE& primaryKey )
         {
             T* result = NULL;
             sqlite3_stmt *stmt;
@@ -48,7 +81,7 @@ class SqliteTools
                 std::cerr << sqlite3_errmsg( dbConnection ) << std::endl;
                 return result;
             }
-            sqlite3_bind_int( stmt, 1, primaryKey );
+            Traits<KEYTYPE>::Bind( stmt, 1, primaryKey );
             if ( sqlite3_step( stmt ) != SQLITE_ROW )
                 return result;
             result = new T( dbConnection, stmt );