如何分配字符串在TypeScript中未定义为字符串? [英] How to assign string | undefined to string in TypeScript?
问题描述
我想分配一个变量,它是字符串|未定义,则为字符串变量,如您在此处看到的:
I want to assign a variable, which is string | undefined, to a string variable, as you see here:
private selectedSerialForReplace(): string | undefined {
return this.selectedSerials.pop();
}
luminaireReplaceLuminaire(params: { "serial": string; "newserial": string; }, options?: any): FetchArgs {
............
}
luminaireReplaceLuminaire({serial: this.selectedSerialForReplace(), newserial: response.output});
我收到此错误:
'{类型的参数:serial:字符串|不明确的;新闻:任何; }' 是 不可分配给类型'{"serial"的参数:字符串; 新闻": 细绳; }'
Argument of type '{ serial: string | undefined; newserial: any; }' is not assignable to parameter of type '{ "serial": string; "newserial": string; }'
我无法将selectedSerialForReplace()函数更改为返回其他任何内容.你能帮我吗?
I cannot change selectedSerialForReplace() function to return anything else. Could you please help me?
推荐答案
打字稿编译器执行严格的空检查,这意味着您不能将string | undefined
变量传递给需要string
的方法.
The typescript compiler performs strict null checks, which means you can't pass a string | undefined
variable into a method that expects a string
.
要解决此问题,您必须在调用luminaireReplaceLuminaire()
之前对undefined
进行显式检查.
To fix this you have to perform an explicit check for undefined
before calling luminaireReplaceLuminaire()
.
在您的示例中:
private selectedSerialForReplace(): string | undefined {
return this.selectedSerials.pop();
}
luminaireReplaceLuminaire(params: { "serial": string; "newserial": string; }, options?: any): FetchArgs {
............
}
const serial = this.selectedSerialForReplace();
if(serial !== undefined) {
luminaireReplaceLuminaire({serial, newserial: response.output});
}
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