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November 13, 2020 02:56
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简化的observable, 帮助理解observable.
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type Unsubscribe = () => void | |
const NOOP: Unsubscribe = () => {} | |
interface Observer<T> { | |
(t: T): void | |
} | |
interface Observable<T> { | |
(ob: Observer<T>): Unsubscribe | |
} | |
class Subject<T> { | |
private subscriptions: Set<Observer<T>> | |
next: Observer<T> = (val: T) => { | |
this.subscriptions.forEach(x => x(val)) | |
} | |
// is complete really necessary? why not just let gc collect it? | |
// complete() { | |
// this.subscriptions.clear() | |
// } | |
subscribe: Observable<T> = (observer: Observer<T>) => { | |
this.subscriptions.add(observer) | |
return () => { | |
this.subscriptions.delete(observer) | |
} | |
} | |
} | |
type Operator<T1, T2> = (ob1: Observable<T1>) => Observable<T2> | |
type SecondOrderOperator<T1, T2, T3, T4> = (op1: Operator<T1, T2>) => Operator<T3, T4> | |
const catchError: <T1, T2>(handler: (error: unknown, unsubscribe: Unsubscribe) => Observable<T1>) => SecondOrderOperator<T1, T2, T1, T2> = handler => op1 => { | |
return ob1 => { | |
const ob2 = op1(obv1 => { | |
const unsub = ob1(val => { | |
try { | |
obv1(val) | |
} catch (err) { | |
handler(err, unsub) | |
} | |
}) | |
return unsub | |
}) | |
return ob2 | |
} | |
} | |
const fromInterval: (ms: number) => Observable<number> = ms => observer => { | |
const unsub = () => { | |
clearInterval(i) | |
console.log("interval cleared") | |
} | |
// const next = observer(() => { | |
// clearInterval(i) | |
// }) | |
let counter = 0 | |
const i = setInterval(() => { | |
observer(counter++) | |
}, ms) | |
return unsub | |
} | |
const take: <T1>(num: number) => Operator<T1, T1> = num => source => { | |
var cur = 0 | |
return sink => { | |
const unsubscribe = source(val => { | |
cur++ | |
if (cur <= num) { | |
sink(val) | |
} else { | |
unsubscribe() | |
} | |
}) | |
return unsubscribe | |
} | |
} | |
const of: <T>(val: T) => Observable<T> = val => next => { | |
next(val) | |
return NOOP | |
} | |
const map: <T1, T2>(fmap: (t: T1) => T2) => Operator<T1, T2> = fmap => source => sink => source(val => sink(fmap(val))) | |
const pipe: <T1, T2, T3>(op1: Operator<T1, T2>, op2: Operator<T2, T3>) => Operator<T1, T3> = (op1, op2) => ob1 => op2(op1(ob1)) | |
const unsub = pipe( | |
() => fromInterval(1000), | |
map(num => { | |
if (num >= 5) { | |
console.log("we have unsubed") | |
unsub() | |
} | |
return num + 1 | |
}) | |
)(of(null))(val => { | |
console.log(val) | |
}) | |
console.log("are we here") |
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哈哈哈哈这居然他妈能跑