TypeScript高级类型检查

Question

请检查代码中的注释。有可能得到我想要的东西吗？或者TS没有这样的功能？

我需要对addToRegistry函数进行类型检查。

TypeScript游乐场，代码

type MessageHandler<T> = ((data: T) => void) | ((data: T) => Promise<void>);
interface AuthPayload {
id: string;
}
class HandlersRegistry {
auth?: MessageHandler<AuthPayload>;
test?: MessageHandler<number>;
}
const registry = new HandlersRegistry();
// handler type should ref on HandlersRegistry[key] by eventType
// function addToRegistry<T>(eventType: keyof HandlersRegistry, handler: ???) {
function addToRegistry<T>(eventType: keyof HandlersRegistry, handler: MessageHandler<T>) {
registry[eventType] = handler; // should not be an error
}
const authHandler: MessageHandler<AuthPayload> = (data: AuthPayload) => null;
// correct
addToRegistry('auth', authHandler);
// correct, shows error, but I don't want to provide type of payload every time
addToRegistry<number>('test', authHandler);
// should show error, but doesn't
addToRegistry('test', authHandler);

谢谢你的回答！

Answer 1

您可以使用泛型类型来保存键的类型，而用于指定参数的类型查询必须与字段类型相同：

type MessageHandler<T> = ((data: T) => void) | ((data: T) => Promise<void>);
interface AuthPayload {
id: string;
}
class HandlersRegistry {
auth?: MessageHandler<AuthPayload>;
test?: MessageHandler<number>;
}
const registry = new HandlersRegistry();
// handler type should ref on HandlersRegistry[key] by eventType
// function addToRegistry<T>(eventType: keyof HandlersRegistry, handler: ???) {
function addToRegistry<K extends keyof HandlersRegistry>(eventType: K, handler: HandlersRegistry[K]) {
registry[eventType] = handler; // should not be an error
}
const authHandler: MessageHandler<AuthPayload> = (data: AuthPayload) => null;
// correct
addToRegistry('auth', authHandler);
// correct, shows error, but I don't want to provide type of payload every time
addToRegistry<number>('test', authHandler);
// show error as expected
addToRegistry('test', authHandler);