docs: 样式

Chapter1 - iOS/1.40.md

@@ -142,22 +142,28 @@ self.shouldStopRun = NO;
 0x1 和 0xa0 是十六进制的数，对应十进制为1和160。
 
 
-
-
-
-参考文章：
-
-http://www.cocoachina.com/ios/20180515/23380.html
-
-http://www.cocoachina.com/ios/20170417/19075.html
-
-https://www.jianshu.com/p/4c38d16a29f1
-
-https://www.cnblogs.com/kenshincui/p/6823841.html
-
-https://juejin.im/entry/599c13bc6fb9a0248926a77d
-
-https://blog.ibireme.com/2015/05/18/runloop/
+## RunLoop 空闲时做一些任务
+```
+- (void)print
+{
+    NSLog(@"test");
+}
+
+- (void)viewDidLoad
+{
+    CFRunLoopActivity flags = kCFRunLoopBeforeWaiting;
+    CFRunLoopObserverRef runloopObserver = CFRunLoopObserverCreateWithHandler(
+        kCFAllocatorDefault, flags, YES, 0,
+        ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
+            [self performSelector:@selector(print)
+                         onThread:[NSThread mainThread]
+                       withObject:nil
+                    waitUntilDone:NO
+                            modes:@[ NSDefaultRunLoopMode ]];
+        });
+    CFRunLoopAddObserver(CFRunLoopGetCurrent(), runloopObserver, kCFRunLoopDefaultMode);	 
+}
+```