iosdevzone · May 30, 2013 08:17 · May 30, 2013
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,22 @@
+#define S(_s) @selector(application##_s:) // selector generator
+#define N(_n) UIApplication##_n##Notification // name generator
+#define L(X) X(WillResignActive), X(DidEnterBackground), \
+X(WillEnterForeground), X(DidBecomeActive), X(WillTerminate) // apply X over list
+#define C(_a) sizeof((_a))/sizeof((_a)[0]) // array count
+
+- (void)monitorAppState:(BOOL)start
+{
+
+    NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
+    SEL s[] = { L(S) };
+    NSString* n[] = { L(N) };
+    NSAssert(C(n) == C(s), @"Name and selector arrays have same size.");
+    for(NSUInteger i = 0; i < C(n); ++i)
+        if([self respondsToSelector:s[i]])
+        {
+            if(start)
+                [nc addObserver:self selector:s[i] name:n[i] object:nil];
+            else
+                [nc removeObserver:self name:n[i] object:nil];
+        }
+}