在Typescript中使用Observable的XMLHttpRequest

Question

当我尝试管理我上传文件的XMLHttpRequest调用的结果时,我遇到了一个tslint问题.这是我在互联网上找到的当前方法:

// Files upload request
makeFileRequest(url: string, files: Array<File>) {
    return new Promise((resolve, reject) => {
        let formData: any = new FormData()
        let xhr = new XMLHttpRequest()
        for(let file of files) {
            formData.append("uploads[]", file, file.name)
        }
        xhr.onreadystatechange = function () {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    resolve(JSON.parse(xhr.response))
                } else {
                    reject(xhr.response)
                }
            }
        }
        xhr.open("POST", url, true)
        xhr.send(formData)
    })
}

所以它工作,文件正在上传,后端回复200响应.但在我使用此函数的方法中,我这样做:

        this.makeFileRequest("theurl", this.listFiles)
        .map(res => res.json())
            .subscribe(
                res => console.log(res),
                error => console.log("fails")
            )

但tslint在地图点告诉我这个:

TS2339 Property 'map' does not exist on type 'Promise<{}>'.

所以我认为管理makeFileRequest函数会更好,所以它返回一个Observable而不是Promise.为了以防万一,请注意我导入"rxjs/add/operator/map".

有谁有任何想法？谢谢 !

Answer 1

map是一种方法Observable,而不是Promise.返回Observable将修复错误:

makeFileRequest(url: string, files: Array<File>) {
    return Observable.fromPromise(new Promise((resolve, reject) => {
        let formData: any = new FormData()
        let xhr = new XMLHttpRequest()
        for (let file of files) {
            formData.append("uploads[]", file, file.name)
        }
        xhr.onreadystatechange = function () {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    resolve(JSON.parse(xhr.response))
                } else {
                    reject(xhr.response)
                }
            }
        }
        xhr.open("POST", url, true)
        xhr.send(formData)
    }));
}

错误的解决方案:

Property 'json' does not exist on type '{}'

/sf/answers/2374392821/

别忘了导入Response:

import {Response} from '@angular/http';