我想在Typescript对象中存储string ->字符串的映射,并强制所有值映射到字符串。例如:

var stuff = {};
stuff["a"] = "foo";   // okay
stuff["b"] = "bar";   // okay
stuff["c"] = false;   // ERROR!  bool != string

是否有一种方法让我强制值必须是字符串(或任何类型..)?


当前回答

type KeyOf<T> = keyof T;

class SomeClass<T, R> {
  onlyTFieldsAllowed = new Map<KeyOf<T>, R>();
}

class A {
  myField = 'myField';
}

const some = new SomeClass<A, any>();

some.onlyTFieldsAllowed.set('myField', 'WORKS');
some.onlyTFieldsAllowed.set('noneField', 'Not Allowed!');

其他回答

基于@shabunc的答案,这将允许将键或值(或两者都是)强制为您想强制的任何值。

type IdentifierKeys = 'my.valid.key.1' | 'my.valid.key.2';
type IdentifierValues = 'my.valid.value.1' | 'my.valid.value.2';

let stuff = new Map<IdentifierKeys, IdentifierValues>();

也应该使用enum而不是类型定义。

你可以传递一个名字给未知键,然后写你的类型:

type StuffBody = {
  [key: string]: string;
};

现在你可以在你的类型检查中使用它:

let stuff: StuffBody = {};

但对于FlowType,不需要有名称:

type StuffBody = {
  [string]: string,
};
interface AccountSelectParams {
  ...
}
const params = { ... };

const tmpParams: { [key in keyof AccountSelectParams]: any } | undefined = {};
  for (const key of Object.keys(params)) {
    const customKey = (key as keyof typeof params);
    if (key in params && params[customKey] && !this.state[customKey]) {
      tmpParams[customKey] = params[customKey];
    }
  }

如果你明白这个概念,请评论

type KeyOf<T> = keyof T;

class SomeClass<T, R> {
  onlyTFieldsAllowed = new Map<KeyOf<T>, R>();
}

class A {
  myField = 'myField';
}

const some = new SomeClass<A, any>();

some.onlyTFieldsAllowed.set('myField', 'WORKS');
some.onlyTFieldsAllowed.set('noneField', 'Not Allowed!');
var stuff: { [key: string]: string; } = {};
stuff['a'] = ''; // ok
stuff['a'] = 4;  // error

// ... or, if you're using this a lot and don't want to type so much ...
interface StringMap { [key: string]: string; }
var stuff2: StringMap = { };
// same as above