From d521b9e605e8153096a377b60b412514f7adbdfd Mon Sep 17 00:00:00 2001
From: Javier Sancho <jsf@jsancho.org>
Date: Sat, 14 Sep 2013 08:27:46 +0200
Subject: [PATCH] Functions to access entities and components inside systems

* src/system.scm: get-key
                  get-component

* src/examples/making-systems.scm: access functions testing
---
 src/examples/making-systems.scm | 17 +++++++++++++++--
 src/system.scm                  | 13 +++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/examples/making-systems.scm b/src/examples/making-systems.scm
index 3709719..0addc1b 100644
--- a/src/examples/making-systems.scm
+++ b/src/examples/making-systems.scm
@@ -22,14 +22,27 @@
 
 (define-component a x y)
 
+(define-system (s1)
+  (lambda (e)
+    (list (new-entity (make-a 1 2))
+	  (new-entity (make-a 10 20)))))
+
+(define-system (s2 a)
+  (lambda (e)
+    (for-each
+     (lambda (e1)
+       (format #t "Key: ~a  Component: ~a~%" (get-key e1) (get-component 'a e1)))
+     e)
+    '()))
+
 (define (making-systems)
   (let ((entities '())
 	(components '()))
-    (receive (e c) (((make-system () (lambda (e) (list (new-entity (make-a 1 2)) (new-entity (make-a 10 20))))) entities components))
+    (receive (e c) ((s1 entities components))
 	     (set! entities e)
 	     (set! components c))
     (format #t "Two new entities with a:~%~a~%~a~%~%" entities components)
 
-    (((make-system (a) (lambda (e) (display e) (newline) '())) entities components))))
+    ((s2 entities components))))
 
 (export making-systems)
diff --git a/src/system.scm b/src/system.scm
index 2a9365b..587fc06 100644
--- a/src/system.scm
+++ b/src/system.scm
@@ -225,3 +225,16 @@
 	make-system
 	join-systems
 	threaded-systems)
+
+
+;;; Entities and components access inside systems
+
+(define (get-key entity)
+  (car entity))
+
+(define (get-component component-name entity)
+  (assoc-ref (cdr entity) component-name))
+
+
+(export get-key
+	get-component)
-- 
2.39.5