英文:
How to infer signature of property based on another property type?
问题
type AnimalType = "dog" | "fish";
interface DogMoveProps {
legs: number;
}
interface FishMoveProps {
fins: number;
}
interface Animal {
type: AnimalType;
move: (props: AnimalType extends "dog" ? DogMoveProps : FishMoveProps) => void;
}
const dog: Animal = {
type: "dog",
move(props) { // DogMoveProps should be automatically inferred
// props.legs
}
}
英文:
Consider the following example:
type AnimalType = "dog" | "fish";
interface DogMoveProps {
legs: number;
}
interface FishMoveProps {
fins: number;
}
interface Animal {
type: AnimalType;
move: (props) => void; // How should this be typed?
}
How can I enforce the type of props based on the value of Animal.type field?
const dog: Animal = {
type: "dog",
move(props) { // <-- DogMoveProps should be automatically inferred
// props.legs
}
}
答案1
得分: 1
你可以定义 AnimalType 和其关联的 Props 类型之间的映射，然后使用自索引的 mapped type 来自动创建基于该映射的 discriminated union：
type AnimalType = "dog" | "fish";
interface DogMoveProps {
legs: number;
}
interface FishMoveProps {
fins: number;
}
type MoveProps = {
"dog": DogMoveProps;
"fish": FishMoveProps;
};
type Animal = {
[K in AnimalType]: {
type: K,
move: (props: MoveProps[K]) => void;
}
}[AnimalType];
const dog: Animal = {
type: "dog",
move(props) {
props.legs
}
};
英文:
You could define a mapping between AnimalType and their associated Props types, and then use a self-indexing mapped type to automatically create a discriminated union based on that mapping:
type AnimalType = "dog" | "fish";
interface DogMoveProps {
legs: number;
}
interface FishMoveProps {
fins: number;
}
type MoveProps = {
"dog": DogMoveProps;
"fish": FishMoveProps;
};
type Animal = {
[K in AnimalType]: {
type: K,
move: (props: MoveProps[K]) => void;
}
}[AnimalType];
const dog: Animal = {
type: "dog",
move(props) {
props.legs
}
};
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