iOS JavaScriptCore与H5交互时出现异常提示

在利用JavaScriptCore与H5交互时出现异常提示：

This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.  This will cause an exception in a future release.

从字面意思看，是因为在后台线程修改了UI，于是乎开始验证

_weak typeof(self)weakSelf = self;

    JSContext *tContext = [weakSelf.webView valueForKeyPath:@"documentView.webView.mainFrame.javaScriptContext"];

    tContext[@"jsredirect"] = ^(){

        NSArray *tArgs = [JSContext currentArguments];
        JSValue *tJSValue = [tArgs firstObject];

        @try
        {
            NSDictionary *tActionValueDic = [tJSValue toDictionary];

            NSLog(@"JSValue:%@", tActionValueDic);

            NSString *tUrlStr = tActionValueDic[@"url"];

            if ([tUrlStr isEqualToString:@"chartDispose"]) {
                [[NSUserDefaults standardUserDefaults] setInteger:0 forKey:@"WebKitCacheModelPreferenceKey"];
                [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"WebKitDiskImageCacheEnabled"];
                [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"WebKitOfflineWebApplicationCacheEnabled"];
                [[NSUserDefaults standardUserDefaults] synchronize];
            }else{
                CGGradeJumpWebViewController *vc = [[CGGradeJumpWebViewController alloc]init];
                vc.urlStr = tUrlStr;
                NSLog(@"Current Thread:%@",[NSThread currentThread]);
                dispatch_async(dispatch_get_main_queue(), ^{
                    //UI修改
                    NSLog(@"Current Thread:%@",[NSThread currentThread]);
                    [weakSelf.navigationController pushViewController:vc animated:YES];
                });
            }

        }
        @catch (NSException *exception)
        {
            NSLog(@"exception:%@", exception);
        }
    };

果然，在XCode7中网页交互实在后台线程中执行的(XCode6木有问题)，所以在交互时修改UI要再主线程中执行，问题解决。