[英]How to annotate generator functions in typescript
Let's look at the example async
function from promisejs.org , which is allows us to wait for promises using generators: 让我们看看promisejs.org中的示例
async
函数,它允许我们使用生成器等待promises:
function async(makeGenerator){
return function () {
var generator = makeGenerator.apply(this, arguments);
function handle(result){
// result => { done: [Boolean], value: [Object] }
if (result.done) return Promise.resolve(result.value);
return Promise.resolve(result.value).then(function (res){
return handle(generator.next(res));
}, function (err){
return handle(generator.throw(err));
});
}
try {
return handle(generator.next());
} catch (ex) {
return Promise.reject(ex);
}
}
}
Example usage: 用法示例:
var login = async(function* (username, password, session) {
var user = yield getUser(username);
var hash = yield crypto.hashAsync(password + user.salt);
if (user.hash !== hash) {
throw new Error('Incorrect password');
}
session.setUser(user);
});
My question: How should both of these functions be annotated in TypeScript, in orded to keep type safety? 我的问题:如何在TypeScript中注释这两个函数,以保持类型安全?
What I've tried: I know the async
function returns a Promise<T>
, but I'm not sure what T
should be. 我试过的:我知道
async
函数返回一个Promise<T>
,但我不确定T
应该是什么。 I guess it should depend on the generator passed in, but what type does a generator have? 我想这应该取决于传入的发电机,但发电机有什么类型? There is
GeneratorFunction
in the typings for nodejs or bluebird (can't remember which), but that one is not generic so I can't do async(makeGenerator: GeneratorFunction<T>): Promise<T>
as I'd want to. nodejs或bluebird的输入中有
GeneratorFunction
(不记得哪个),但那个不是通用的,所以我不能做async(makeGenerator: GeneratorFunction<T>): Promise<T>
因为我想要。
but I'm not sure what T should be
但我不确定T应该是什么
In your case login
returns nothing to Promise<void>
. 在您的情况下,
login
不向Promise<void>
返回任何内容。
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