有没有办法让这样的代码编译并保持类型安全?
type ComplexObject = {
primitive1: boolean;
complex: {
primitive2: string;
primitive3: boolean;
}
};
interface MyReference {
myKey: keyof ComplexObject;
}
const works1: MyReference = {
myKey: "primitive1"
}
const works2: MyReference = {
myKey: "complex"
}
const iWantThisToCompile1: MyReference = {
myKey: "complex.primitive2" // Error: Type '"complex.primitive2"' is not assignable to type '"primitive1" | "complex"'.
}
const iWantThisToCompile2: MyReference = {
myKey: "complex['primitive3']" // Error: Type '"complex['primitive3']"' is not assignable to type '"primitive1" | "complex"'.
}
// const iDontWantThisToCompile1: MyReference = {
// myKey: "primitive2"
// }
// const iDontWantThisToCompile2: MyReference = {
// myKey: "primitive3"
// }
您可以在此处使用此代码。
使用TypeScript 4.1中的新模板文字类型和递归类型,可以做到这一点。
这里有几种定义此方法的方法,它们可以作用于单个级别。我建议第一种方法,因为它的公共API中没有其他未使用的类型参数。
export type RecursiveKeyOf<TObj extends object> = {
[TKey in keyof TObj & (string | number)]:
RecursiveKeyOfHandleValue<TObj[TKey], `${TKey}`>;
}[keyof TObj & (string | number)];
type RecursiveKeyOfInner<TObj extends object> = {
[TKey in keyof TObj & (string | number)]:
RecursiveKeyOfHandleValue<TObj[TKey], RecursiveKeyOfAccess<TKey>>;
}[keyof TObj & (string | number)];
type RecursiveKeyOfHandleValue<TValue, Text extends string> =
TValue extends object
? Text | `${Text}${RecursiveKeyOfInner<TValue>}`
: Text;
type RecursiveKeyOfAccess<TKey extends string | number> =
| `['${TKey}']`
| `.${TKey}`;
export type RecursiveKeyOf<TObj extends object, isFirstLevel extends boolean = true> = {
[TKey in keyof TObj & (string | number)]:
isFirstLevel extends true
? RecursiveKeyOfHandleValue<TObj[TKey], `${TKey}`>
: RecursiveKeyOfHandleValue<TObj[TKey], RecursiveKeyOfAccess<TKey>>;
}[keyof TObj & (string | number)];
type RecursiveKeyOfHandleValue<TValue, Text extends string> =
TValue extends object
? Text | `${Text}${RecursiveKeyOf<TValue, false>}`
: Text;
type RecursiveKeyOfAccess<TKey extends string | number> =
| `['${TKey}']`
| `.${TKey}`;
如果只需要属性访问,则要简单得多:
export type RecursiveKeyOf<TObj extends object> = {
[TKey in keyof TObj & (string | number)]:
TObj[TKey] extends object
? `${TKey}` | `${TKey}.${RecursiveKeyOf<TObj[TKey]>}`
: `${TKey}`;
}[keyof TObj & (string | number)];
export type RecursiveKeyOf<TObj extends object> = (
(
// 1. Create an object type from `TObj`, where all the individual
// properties are mapped to a string type if the value is not an object
// or union of string types containing the current and descendant
// possibilities when it's an object type.
{
// Does this for every property in `TObj` that is a string or number
[TPropName in keyof TObj & (string | number)]:
HandleProperty<TObj[TPropName], TPropName>;
}
)[
keyof TObj & (string | number) // for every string or number property name
] // 2. Now flatten the object's property types to a final union type
);
type HandleProperty<TValue, TPropName extends string | number> =
// If the value of the property is an object type...
TValue extends object
// Then...
// 1. Return the current property name as a string
? `${TPropName}`
// 2. And return the property name concatenated with a `.` and
// all the return values of `RecrusiveKeyOf<TValue>`
| `${TPropName}.${RecursiveKeyOf<TValue>}`
// Else, only return the current property name as a string
: `${TPropName}`;
例如:
// this type
{
prop: { a: string; b: number; };
other: string;
}
// goes to
{
prop: "prop" | "prop.a" | "prop.b";
other: "other";
}
// goes to
"prop" | "prop.a" | "prop.b" | "other"
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