javascript – 无法在回调函数中调用任何fineUploader方法

我将autoUpload设置为false,因为我想将图像自己上传到我的后端.但是,要做到这一点,我首先需要文件对象.在回调onSubmitted事件中,我试图将图像id传递给getFile方法,以返回该对象.但是,当我尝试这样做时,我收到以下错误消息.

in onSubmitted: id=0 | name=28603454_15219061700_r.jpg index.js:2178

[Fine Uploader 5.16.2] Caught exception in ‘onSubmitted’ callback –
Cannot read property ‘uploader’ of null

我猜我得到了这个,因为我正在声明一个const对象并同时引用它,我相信你做不到…

那么,关于如何在回调函数中调用方法的任何想法？或者还有另一种方式吗？

const uploader = new FineUploaderTraditional({
  options: {
    maxConnections: 1,
    autoUpload: false,
    deleteFile: { enabled: true, endpoint: "/uploads" },
    request: { endpoint: "/uploads" },
    retry: { enableAuto: true },
    callbacks: {
      onSubmitted: function(id, name) {
        console.log("in onSubmitted: id=" + id + " | name=" + name);
        // getFile(id) returns a `File` or `Blob` object.
        console.log(this.uploader.getFile(id));
      }
    }
  }
});

更新
我现在已经完成了所有的上传代码并用它创建了一个新的组件.我仍然面临同样的问题.组件代码如下：

FineUploader.jsx

import React, { Component } from "react";
import FineUploaderTraditional from "fine-uploader-wrappers";
import Gallery from "react-fine-uploader";
import Filename from "react-fine-uploader/filename";
import "react-fine-uploader/gallery/gallery.css";

const util = require("util");

const uploader = new FineUploaderTraditional({
  options: {
    // debug: true,
    maxConnections: 1,
    autoUpload: false,
    deleteFile: { enabled: true, endpoint: "/uploads" },
    request: { endpoint: "/uploads" },
    retry: { enableAuto: true },
    validation: {
      acceptFiles: ".jpg,.png,.gif,.jpeg",
      allowedExtensions: ["jpg", "png", "gif", "jpeg"],
      itemLimit: 5,
      sizeLimit: 5000000
    },
    callbacks: {
      onCancel: function() {
        console.log("in onCancel: ");
      },
      onComplete: function(id, name, responseJSON, xhr) {
        console.log("in onComplete: " + id + " | " + name + " | " + responseJSON + " | " + xhr);
      },
      onAllComplete: function(succeeded, failed) {
        console.log("in onAllComplete: " + succeeded + " | " + failed);
      },
      onProgress: function(id, name, uploadedBytes, totalBytes) {
        console.log("in onProgress: " + id + " | " + name + " | " + uploadedBytes + " | " + totalBytes);
      },
      one rror: function(id, name, errorReason, xhr) {
        console.log("in one rror: " + id + " | " + name + " | " + errorReason + " | " + xhr);
      },
      onDelete: function(id) {
        console.log("in onDelete: " + id);
      },
      onDeleteComplete: function(id, xhr, isError) {
        console.log("in onDeleteComplete: " + id + " | " + xhr + " | " + isError);
      },
      onPasteReceived: function(blob) {
        console.log("in onPasteReceived: " + blob);
      },
      onResume: function(id, name, chunkData, customResumeData) {
        console.log("in onResume: " + id + " | " + name + " | " + chunkData + " | " + customResumeData);
      },
      onStatusChange: function(id, oldStatus, newStatus) {
        console.log("in onStatusChange: " + id + " | " + oldStatus + " | " + newStatus);
      },
      onSubmit: function(id, name) {
        console.log("in onSubmit: " + id + " | " + name);
      },
      onSubmitted: function(id, name) {
        console.log("in onSubmitted: id=" + id + " | name=" + name);
        // getFile(id) returns a `File` or `Blob` object.
        // console.log(this.uploader.getFile(id));
        // console.log(uploader.getFile(id));
        // nothing here is working.... :(
      },
      onUpload: function(id, name) {
        console.log("in onUpload: " + id + " | " + name);
      },
      onValidate: function(data, buttonContainer) {
        console.log(
          "in onValidate: " + util.inspect(data, { showHidden: true, depth: null }) + " | " + buttonContainer
        );
      },
      onSessionRequestComplete: function(response, success, xhrOrXdr) {
        console.log("in onSessionRequestComplete: " + response + " | " + success + " | " + xhrOrXdr);
      }
    }
  }
});

const fileInputChildren = <span>Click to Add Photos</span>;
const statusTextOverride = {
  upload_successful: "Success!"
};

class FineUploader extends Component {
  constructor() {
    super();

    this.state = {
      submittedFiles: []
    };
  }

  componentDidMount() {
    uploader.on("submitted", id => {
      const submittedFiles = this.state.submittedFiles;
      console.log("submittedFiles: " + submittedFiles);

      submittedFiles.push(id);
      this.setState({ submittedFiles });
    });
  }

  render() {
    return (
      <div>
        {this.state.submittedFiles.map(id => (
          <Filename id={id} uploader={uploader} />
        ))}
        <Gallery
          fileInput-children={fileInputChildren}
          status-text={{ text: statusTextOverride }}
          uploader={uploader}
        />
      </div>
    );
  }
}

export default FineUploader;

而且 – 现在在主页上,我正在导入FineUploader.jsx,并使用该组件.

import FineUploader from "../../components/FineUploader";

在我的渲染方法中,我有：

<FineUploader />

解决方法:

这在javascript中很棘手.在常规函数内(例如,函数f(){…}),这取决于调用函数的位置而不是函数的定义位置.当通过第三方API使用回调时,您实际上无法控制它的调用位置,因此最终可能会出现上述错误.

幸运的是,您可以使用箭头函数(例如,const f =()=> {…};)根据函数的定义位置绑定它.

有关详细信息,请参阅MDN docs,或者您可以参考this excellent SO answer.

但是,对于您的代码,我不确定当您定义onSubmitted时,其中任何一个都可以作为您的全局/窗口对象.

为了使其工作,您需要在顶层创建一个闭包(在您实际创建上传器之前)：

function onSubmitted(id, name) {
    console.log("in onSubmitted: id=" + id + " | name=" + name);
    // getFile(id) returns a `File` or `Blob` object.
    console.log(uploader.getFile(id));
}

const uploader = new FineUploaderTraditional({..., callbacks: {onSubmitted, ...}});

这将允许您在实际实例化之前定义与上传器交互的逻辑(这是您想要的样子).注意缺少这个,因为我们只是利用js闭包规则.

标签：javascript,reactjs,callback,fine-uploader
来源： https://codeday.me/bug/20190627/1303708.html