Question

我正在向Angular发送数据，但记录的值（关闭日期）之一为null。如何在Angular中处理此问题，以便如果value为null，则更改为--

  getDetails() {
    this.myService.getFlowerDetails(this.flowerId, this.flowerName).subscribe(
      res => {
        this.flower = res;
        if(this.flower !== undefined){
          this.flowerName = this.flower.flowerName;
          this.flowerId = this.flower.flowerId.toString();
          this.flowerCategory = this.flower.flowerCategory;
          this.recordCreateDate = this.flower.recordCreateDate.toString();
          this.recordClosedDate = this.flower.recordClosedDate.toString(); // this is null in the backend
        }
        else{
          this.flowerName = "--";
          this.flowerId = "--";
          this.flowerCategory = "--";
          this.recordCreateDate = "--";
          this.recordClosedDate = "--";
        }
      }, er => {
    this.throwError = er;
});

我收到以下错误。这不是整个堆栈跟踪（不确定是否需要）

TypeError

columnNumber: 17

fileName: "http://localhost:4200/main.bundle.js"

lineNumber: 1738

message: "_this.flower.recordClosedDate is null"

Answer 1

如果||是假的（this.flower.recordClosedDate，undefined，空字符串，零，则null运算符可用于设置默认值：

this.recordClosedDate = (this.flower.recordClosedDate || "--").toString();

Answer 2

普通的?:三元运算符怎么样：

this.recordClosedDate = this.flower.recordClosedDate !=null ?  this.flower.recordClosedDate : "--"

如何在Angular中处理空值

2 个答案: