我想从https://api.exchangeratesapi.io/latest获取CAD值，我已经使用了很多类型的代码，它说"TypeError: Cannot read property 'CAD' of undefined"确实需要您的帮助，非常感谢。
如果我管理此代码，它将输出所有货币
((this.state.data as any).rates)
但是当我想获取CAD货币时，会显示错误
我已经尝试过这些代码：
((this.state.data as any).rates as any).CAD
(this.state.data as any)["Rates"]["CAD"];
(this.state.data as any)["Rates"].CAD;
我获取数据的方式是
interface IState {
data?: object | null;
isCurrency?: boolean;
Currency?: string;
Rate?: number;
}
export default class Header extends Component<{}, IState> {
service: UserService = new UserService();
state = {
isCurrency: false,
Currency: "USD",
Rate: 1,
data: [] = []
};
async componentDidMount() {
let result = await this.service.getAllCurrency();
this.setState({
data: (result as Pick<IState, keyof IState>).data
});
console.log(result);
}
}
1.4591（基于最新的API）
您应该为数据创建一个类型。因为它来自外部来源，所以打字稿无法推断出来。然后解析您的JSON并将其转换为该类型。
// Create a type for the expernal data.
interface Data {
rates: {
[currency: string]: number
}
base: string
date: string
}
// Result of `JSON.parse()` will be `any`, since typescript can't parse it.
const untypedData = JSON.parse(`{
"rates": {
"CAD": 1.4591,
"HKD": 8.6851,
"ISK": 135.9,
"PHP": 56.797,
"DKK": 7.4648
},
"base": "EUR",
"date": "2019-07-25"
}`)
// Cast the untyped JSON to the type you expect it to be.
const data: Data = untypedData
// Use the data according to it's type.
alert(data.rates.CAD)
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我来说两句