如何实现异步验证在2角 [英] How to implement Async Validator in Angular 2

问题描述

1 难道甚至角支撑了吗？看到这个的悬而未决的问题。

1. Is it even supported by Angular yet ? see this open issue

2 如果是，那么什么是错在下面

2. If it is, then what is wrong in the code below

export class someClass{

    myForm:ControlGroup;

    constructor(public http:Http, public formBuilder:FormBuilder)
       this.myForm = formBuilder.group({
            ImageId: ["", Validators.required, this.asynValidator]
    });

    asyncValidator(control: Control): {[key: string]: any} {

        return new Promise (resolve => {

          let headers = new Headers();
          headers.append('Content-Type', 'application/json');

          this.http.get('http://localhost/ImageIdValidate?id='+ control.value, {headers:headers})
                .map(res => res.json())
                .subscribe(data => {
                    console.log(data);
                    if(data != null) {
                        resolve({"duplicate": true})
                    }
                    else resolve(null);      
                })
            });
        });
      }
    }

它甚至没有一台服务器的请求。

It doesn't even make a server request.

推荐答案

您需要在您的方法绑定组件实例本身的描述如下：

You need to bind your method on the component instance itself as described below:

this.myForm = formBuilder.group({
            ImageId: ["",    
               Validators.required, 
               this.asynValidator.bind(this)]
    });

否则，你将无法使用http属性来执行您的要求。

Otherwise you won't be able to use the http property to execute your request.

本文还可以给你有关异步表单验证一些提示（参见异步验证）：

This article could also give you some hints about asynchronous form validation (see the section "asynchronous validation"):

• 的http://restlet.com/blog/2016/02/17/implementing-angular2-forms-beyond-basics-part-2/

这篇关于如何实现异步验证在2角的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！