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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 28 |
1 files changed, 21 insertions, 7 deletions
@@ -143,7 +143,23 @@ entity.assign<Position>(1.0f, 2.0f); #### Querying entities and their components -To query all entities with a set of components assigned, use ``entityx::EntityManager::entities_with_components()``. This method will return only those entities that have *all* of the specified components associated with them, assigning each component pointer to the corresponding component instance: +To query all entities with a set of components assigned you can use two +methods. Both methods will return only those entities that have *all* of the +specified components associated with them. + +`entityx::EntityManager::each(f) provides functional-style iteration over +`entity components. The callback for `each()` can optionally accept an Entity as +`its first argument. + +```c++ +entities.each<Position, Direction>([](Entity entity, Position &position, Direction &direction) { + // Do things with entity, position and direction. +};) +``` + + +For iterator-style traversal of components, use +``entityx::EntityManager::entities_with_components()``: ```c++ ComponentHandle<Position> position; @@ -189,12 +205,10 @@ A basic movement system might be implemented with something like the following: ```c++ struct MovementSystem : public System<MovementSystem> { void update(entityx::EntityManager &es, entityx::EventManager &events, TimeDelta dt) override { - ComponentHandle<Position> position; - ComponentHandle<Direction> direction; - for (Entity entity : es.entities_with_components(position, direction)) { - position->x += direction->x * dt; - position->y += direction->y * dt; - } + es.each<Position, Direction>([dt](Position &position, Direction &direction) { + position.x += direction.x * dt; + position.y += direction.y * dt; + }); }; }; ``` |