typescript 类型对象上不存在属性“地图”
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Property 'map' does not exist on type Object
提问by kraftwer1
type MyStructure = Object[] |?Object;
const myStructure: MyStructure = [{ foo: "bar" }];
myStructure.map(); // Property 'map' does not exist on type 'MyStructure'. any
The library either delivers an object or an array of this object. How can I type this?
该库要么提供一个对象，要么提供此对象的数组。我怎样才能输入这个？
EDIT
编辑
And how can I access properties like myStructure["foo"]in case of myStructurewill be an object?
我怎样才能访问性能，如myStructure["foo"]在案件的myStructure将是一个对象呢？
回答by Fenton
Because your type means you could have an object, or you could have an array; TypeScript can't determine which members are appropriate.
因为你的类型意味着你可以有一个对象，或者你可以有一个数组；TypeScript 无法确定哪些成员是合适的。
To test this out, change your type and you'll see the mapmethod is now available:
要对此进行测试，请更改您的类型，您将看到该map方法现在可用：
type MyStructure = Object[];
In your case, the actual solution will be to use a type guard to check that you have an array before attempting to use the mapmethod.
在您的情况下，实际的解决方案是在尝试使用该map方法之前使用类型保护来检查您是否有一个数组。
if (myStructure instanceof Array) {
myStructure.map((val, idx, []) => { });
}
You could also solve your problem using a slightly different definition of MyStructure, for example:
您还可以使用稍微不同的 定义来解决您的问题MyStructure，例如：
type MyStructure = any[] | any;
Or the narrower:
或者更窄：
class Test {
foo: string;
}
type MyStructure = Test[] | Test;
