xu::polykey_map<Value_T, Key_Ts...> implements a container analogous to a table in a relational database where:
| Key 1 | Key 2 | Value |
|---|---|---|
| 15 | "Hello" | |
| 'F' | ", " | |
| 16 | 'D' | "World!" |
- There is one value column and multiple nullable key columns
- Each row must have at least one valid key
- Value retrieval is done by specifying a key column and a valid key
- Removal is at the row level, i.e. removing where key1=16 also results in the removal of key='D'
- Keys are unique within a column
Member functions take a column index as a template parameter and a key as a function parameter.
void insert<index>(key, value)Value_T& get<index>(key)bool contains<index>(key)
The link function takes an additional index and key.
void link<index1, index2>(key1, key2)bool is_linked<index1, index2>(key1)Key_T<index2> convert_key<index1, index2>(key1)
New values are inserted with a single key. To add a new key for an existing value, the link function is used.
Example code:
enum Keys
{
Key1,
Key2
};
/* the first template argument is the stored value type */
xu::polykey_map<std::string, int, char> pkmap;
pkmap.insert<Key1>(15, "Hello");
pkmap.insert<Key2>('F', ", ");
pkmap.insert<Key1>(16, "World!");
pkmap.link<Key1, Key2>(16, 'D');
...
pkmap.at<Key2>('D') = "there!"
pkmap.erase<Key1>(16);
if (pkmap.contains<Key1>(17))
{
...
}
for (auto& s : pkmap)
{
...
}