Angularjs 如何将多个图像发布到firebase并获取其下载url？

我正在使用离子3和firebase。我试图上传多个图像一次使用为每个循环。上传它们后，我需要获得下载url以将它们存储在数据库中。由于获取“下载url”部分是异步的，因此在上载图像的.then（）部分后，我必须将数据插入数据库中……我该怎么做？这是我在提交表格后得到的结果：

post_news(form: NgForm){

    this.title = form.value.title;
    this.content = form.value.content;
    this.category = form.value.category;


    console.log(this.capturedimage1);


    if(this.capturedimage1 !== ''){


        this.images_to_upload.push(this.capturedimage1);


    }



    if(this.capturedimage2 !== ''){

        this.images_to_upload.push(this.capturedimage2);
    }

    if(this.capturedimage3 !== ''){

        this.images_to_upload.push(this.capturedimage3);
    }


    if(this.capturedimage4 !== ''){

        this.images_to_upload.push(this.capturedimage4);
    }



    images_url_from_db = [];

    this.images_to_upload.forEach(function(item){


        let storageRef = firebase.storage().ref();

        const filename = Math.floor(Date.now() / 1000);

        const imageRef = storageRef.child(`images/${filename}.jpg`);





     imageRef.putString(item, firebase.storage.StringFormat.DATA_URL).then(data=>{

     images_url_from_db.push(downloadURL);



     });


    })

}

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可能对其他人有用…在玩了很长时间之后，我想出了一种方法…首先，我将非图像数据插入数据库（如标题、内容、类别）。然后我得到插入数据的密钥。然后我使用该键逐个上传图像，这将插入图像url，如image1、image2、image3等等

post_news(form: NgForm){

    this.title = form.value.title;
    this.content = form.value.content;
    this.category = form.value.category;


    this.news = this.afDb.list('/news');
    this.news.push({title: this.title,content: this.content, category: this.category}).then(data=>{

        var item_key = data.key;

        console.log(data.key);

        if(this.capturedimage1 !== ''){

            let storageRef = firebase.storage().ref();

            const filename = Math.floor(Date.now() / 1000);

            const imageRef = storageRef.child(`images/${filename}.jpg`);


            imageRef.putString(this.capturedimage1, firebase.storage.StringFormat.DATA_URL).then(data=>{

            this.news = this.afDb.list('/news');
            this.news.update(item_key, {image1: data.downloadURL}); 


            });
        }


        if(this.capturedimage2 !== ''){

            let storageRef = firebase.storage().ref();

            const filename = 'img'+Math.floor(Date.now() / 1000);

            const imageRef = storageRef.child(`images/${filename}.jpg`);


            imageRef.putString(this.capturedimage2, firebase.storage.StringFormat.DATA_URL).then(data=>{

            this.news = this.afDb.list('/news');
            this.news.update(item_key, {image2: data.downloadURL}); 


            });
        }



        }).then(data=>{



            form.reset();
            this.capturedimage1 = '';
            this.capturedimage2 = '';
            this.navCtrl.parent.select(0);

        });





}