json - 为什么我得到更新的 json 字段转换的信息 ZoneAwarePromise 数据

Question

我正在尝试将“图像 URL 字段”转换为 base64 blob 数据，但是更新的字段控制台日志数据显示为 ZoneAwarePromise {__zone_symbol__state: null, __zone_symbol__value: Array(0)}

this.http.get(this.api).subscribe(data => {
              this.mainContact = data;
              for (var a = 0; a < this.mainContact.length; a++) {
                for (var j = 0; j < this.mainContact[a].acf.project_gallery.length; j++) {
                   var mainUrl = 'https://cdnwebapp.azureedge.net'+this.mainContact[a].acf.project_gallery[j].url;
                  //Below updates the all field value to the converted blob 
                   this.mainContact[a].acf.project_gallery[j].url = this.convertToDataURLviaCanvas(mainUrl, "image/jpeg", 1)
                    .then(base64Img => {                    
                      return  base64Img;
                    // console.log(base64Img);  *As Expected blob*      
                    })
                    //console.log(this.mainContact[a].acf.project_gallery[j].url) * The update field data console log is showing as ZoneAwarePromise

                    } 
            }

      });



    convertToDataURLviaCanvas(url, outputFormat, osize){
        return new Promise( (resolve, reject) => {
          let img = new Image();
          img.crossOrigin = 'Anonymous';
          img.onload = function(){
            let canvas = <HTMLCanvasElement> document.createElement('CANVAS'),
            ctx = canvas.getContext('2d'),
            dataURL;
            canvas.height = 959;
            canvas.width = 1365;
            ctx.drawImage(img, 0, 0);
            dataURL = canvas.toDataURL(outputFormat, osize);
            //callback(dataURL);
            canvas = null;
            resolve(dataURL); 
          };
          img.src = url;
      });
      }

标签： jsonangularpromise

Answer 1

我认为您必须在.then.

尝试：

this.convertToDataURLviaCanvas(mainUrl, "image/jpeg", 1)
                    .then(base64Img => {                    
                      this.mainContact[a].acf.project_gallery[j].url = base64img
                      console.log(base64Img);
                      console.log(this.mainContact[a].acf.project_gallery[j].url);      
                    })