### 问题一 在Angular 2 中报错误： ``` ERROR Error: ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. ``` 解决办法参考： - [Angular 2 detection explained](https://blog.thoughtram.io/angular/2016/02/22/angular-2-change-detection-explained.html) - [Angular 2 Expression Changed After It Has Been Checked Exception](http://www.allenhashkey.com/web-development/angular2/angular-2-expression-changed-after-it-has-been-checked-exception/) ## 问题二 使用ng2-file-upload上传前预览图片 参考： - [Preview an image before it is uploaded](https://stackoverflow.com/questions/4459379/preview-an-image-before-it-is-uploaded) ## 问题三 在Angular2中基于模型驱动动态渲染checkbox组时，不能按照angularjs方式来处理。会涉及到`FormArray`如何使用。 参考： - [Checkbox Group handling and Validation in Angular2](https://stackoverflow.com/questions/39674718/checkbox-group-handling-and-validation-in-angular2)