update readme

README.md

@@ -59,14 +59,22 @@ You can check if methods are really being called in your test cases:
     __block BOOL testCallCalled = NO;
     [testClass aspect_hookSelector:@selector(testCall) atPosition:AspectPositionAfter withBlock:^(id object, NSArray *arguments) {
         testCallCalled = YES;
-    }];
+    } error:NULL];
 
     [testClass2 testCallAndExecuteBlock:^{
         [testClass testCall];
-    }];
+    } error:NULL];
     XCTAssertTrue(testCallCalled, @"Calling testCallAndExecuteBlock must call testCall");
 }
 ```
+-------------------
+It can be really useful for debugging. Here I was curious when exactly the tap gesture changed state:
+
+``` objc
+[_singleTapGesture aspect_hookSelector:@selector(setState:) atPosition:AspectPositionAfter withBlock:^(__unsafe_unretained id object, NSArray *arguments) {
+    NSLog(@"%@: %@", object, arguments);
+} error:NULL];
+```
 
 -------------------
 Another convenient use case is adding handlers for classes that you don't own. I've written it for use in [PSPDFKit](http://pspdfkit.com), where we require notifications when a view controller is being dismissed modally. This includes UIKit view controllers like `MFMailComposeViewController` or `UIImagePickerController`. We could have created subclasses for each of these controllers, but this would be quite a lot of unnecessary code. Aspects gives you a simpler solution for this problem:
@@ -83,7 +91,7 @@ Another convenient use case is adding handlers for classes that you don't own. I
         if (weakSelf.isBeingDismissed) {
             action();
         }
-    }];
+    } error:NULL];
 }
 
 @end
@@ -112,7 +120,7 @@ When you're using Aspects with `AspectPositionInstead`, the last argument of the
             processTouches = pspdf_stylusShouldProcessTouches(arguments[0], arguments[1]);
             [invocation setReturnValue:&processTouches];
         }
-    }];
+    } error:NULL];
 ```
 
 Installation