javascript – ngFor在Angular 2中从promise中填充的对象

我正在使用filesFromZip对象中的blobURL解析带有图像的zip文件,并使用ngFor迭代它以在页面上显示图像.

看起来像这样

filesFromZip = {};let zip = new JSZip();zip.loadAsync(zipfileFromInput)  .then(function (zip) {    for (let file in zip.files) {    let fileInZip = zip.files[file];    zip.file(fileInZip.name)      .async("arraybuffer")      .then(function (content) {        let buffer = new Uint8Array(content);        let blob = new Blob([buffer.buffer]);        // here is where I want to push this object into the filesFromZip object somehow....        return {          fileName: fileInZip.name,          blobURL: URL.createObjectURL(blob)        };    });   }  });

在模板中：

<md-card *ngFor="let file of filesFromZip">  <h3 md-line>{{file.fileName}}</h3>  <img src="{{file.blobURL}}"></md-card>

如何从promiseFromZip获取数据？

我试图将它推入filesFromZip,但这给了我这个错误：

error_handler.js:47 EXCEPTION: Uncaught (in promise): TypeError:
Cannot read property ‘async’ of null

我真的在与异步和Angular 2争吵.有人可以把我送到正确的方向吗？

解决方法:

首先,您不能使用* ngFor指令迭代普通对象,因此filesFromZip应该是一个数组.

this.filesFromZip = [];zip.loadAsync(zipfileFromInput)  .then((zip)=> {    for (let file in zip.files) {      let fileInZip = zip.files[file];      zip.file(fileInZip.name)        .async("arraybuffer")        .then((content)=> {          let buffer = new Uint8Array(content);          let blob = new Blob([buffer.buffer]);          // here is where I want to push this object into the filesFromZip object somehow....          this.filesFromZip.push({            fileName: fileInZip.name,            blobURL: URL.createObjectURL(blob)          });      });   }  });

或者你可以使用Promise.all(),它将从可迭代的Promise中创建一个promise,然后使用异步管道：

javascript：

this.filesFromZip = Promise.all(  zip.loadAsync(zipfileFromInput)    .then((zip)=> {      let out=[];      for (let file in zip.files) {        let fileInZip = zip.files[file];        out.push(zip.file(fileInZip.name)          .async("arraybuffer")          .then((content)=> {            let buffer = new Uint8Array(content);            let blob = new Blob([buffer.buffer]);            // here is where I want to push this object into the filesFromZip object somehow....            this.filesFromZip.push({              fileName: fileInZip.name,              blobURL: URL.createObjectURL(blob)            });        }));    }    return out;    });)

模板：

<md-card *ngFor="let file of filesFromZip|async">  <h3 md-line>{{file.fileName}}</h3>  <img src="{{file.blobURL}}"></md-card>

但是,这里的主要问题似乎是zip.file(fileInZip.name)返回null

来源：https://www.icode9.com/content-1-316651.html