如何使用Rxjs在Angular中调用多个异步方法的数组？

Question

我有具有ivalidator列表的Base Validator方法。

import { IValidator, ValidatorModel } from "../validation/ivalidator";
import { Observable } from "rxjs/Observable";

export abstract class BaseValidator implements IValidator {

    private validators = new Array<IValidator>();

    //Validators are pushed to the base validator =>Not implemented yet

    validate(): Observable<ValidatorModel> {

        for (let i = 0; i < this.validators.length; i++) {
            //How do I loop thru all the validator and call its ASYNC method 
            //one by one and break and return when there is an error ???
        }

    }
}

每个validator方法都公开validate()方法，该方法返回一个可观察值。

export interface IValidator {
    validate(): Observable<ValidatorModel>;
}

ValidatorModel是

export class ValidatorModel {
    readonly isSuccessful: boolean;
    errors: Array<string>;
}

我的问题是：

我如何遍历所有验证器并一个接一个地调用其ASYNC方法，并在出现错误时中断并返回？

Answer 1

如果要一次一次执行验证，请使用merge运算符：

validate(): Observable<ValidatorModel> {
    let obs = this.validators.map(validator=>validator.validate());
    return Observable.merge(obs);
}

如果希望同时并行执行验证，请使用forkJoin运算符：

validate(): Observable<ValidatorModel> {
    let obs = this.validators.map(validator=>validator.validate());
    return Observable.forkJoin(obs);
}

至于错误处理， merge和forkJoin都会在遇到错误时抛出错误，您可以在您的forkJoin subscribe()处理程序中进行处理。 如果您要对Observable<ValidatorModel>做更多的操作，那么错误将被抛出最终的堆栈：

someValidator.subscribe(
            (results) => {
            },
            (error) => {
                //handle error here
            },
            () => {
                //observable completed
            })

如果选择显式处理基类中的错误，请使用catch运算符：

return Observable.forkJoin(obs)
    .catch(error=>{
        console.log('error encountered',error);
        //handle your errors here
        //Return an empty Observable to terminate the stream
        return Observable.empty();
    });