使用NgModel绑定，数字变为字符串 [英] number becomes string using NgModel binding

问题描述

我不理解Typescript和Angular的这种行为.

I don't understand this behaviour with Typescript and Angular.

my-component.html

  <ion-select [(ngModel)]="creditAmount"
              (ngModelChange)="onChangeCreditAmount()">
    <ion-option value="25" selected="true">25€</ion-option>
    <ion-option value="50">50€</ion-option>
    <ion-option value="75">75€</ion-option>
    <ion-option value="100">100€</ion-option>
  </ion-select>

my-component.ts

  creditAmount: number;

  constructor() {
    this.creditAmount = 25;
    console.log(this.creditAmount);
  }
  onChangeCreditAmount() {
    console.log(this.creditAmount);
  }

在构造函数中，creditAmount是一个数字.在 onChangeCreditAmount 方法中，它变成了一个字符串.

In the constructor, creditAmount is a number. In the onChangeCreditAmount method, it became a string.

我发现的唯一解决方法是使用显式强制转换: Number(this.creditAmount)，但这对我来说似乎很棘手.有没有更好的办法 ?谢谢.

The only workaround I found is to use explicit cast: Number(this.creditAmount) but this seems hacky to me. Is there a better way ? Thanks.

推荐答案

Typescript仅有助于编译时.结果仍然是一些JavaScript，这不是类型安全的.因此，您可以为 creditAmount 分配一个数字，一个字符串，一个数组或任何您喜欢的东西.

Typescript only helps on compile time. The result will still be some JavaScript, which is not type safe. So you can assign creditAmount a number, a string, an array or whatever you like.

NgModel 似乎仅适用于字符串，因此如果需要数字，则必须对其进行解析.抱歉:-(

NgModel seems to work with strings only, so you have to parse it if you need a number. Sorry :-(

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