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- import { Observable } from '../Observable';
- import { identity } from '../util/identity';
- import { ObservableInput, SchedulerLike } from '../types';
- import { isScheduler } from '../util/isScheduler';
- import { defer } from './defer';
- import { scheduleIterable } from '../scheduled/scheduleIterable';
- type ConditionFunc<S> = (state: S) => boolean;
- type IterateFunc<S> = (state: S) => S;
- type ResultFunc<S, T> = (state: S) => T;
- export interface GenerateBaseOptions<S> {
- /**
- * Initial state.
- */
- initialState: S;
- /**
- * Condition function that accepts state and returns boolean.
- * When it returns false, the generator stops.
- * If not specified, a generator never stops.
- */
- condition?: ConditionFunc<S>;
- /**
- * Iterate function that accepts state and returns new state.
- */
- iterate: IterateFunc<S>;
- /**
- * SchedulerLike to use for generation process.
- * By default, a generator starts immediately.
- */
- scheduler?: SchedulerLike;
- }
- export interface GenerateOptions<T, S> extends GenerateBaseOptions<S> {
- /**
- * Result selection function that accepts state and returns a value to emit.
- */
- resultSelector: ResultFunc<S, T>;
- }
- /**
- * Generates an observable sequence by running a state-driven loop
- * producing the sequence's elements, using the specified scheduler
- * to send out observer messages.
- *
- * 
- *
- * ## Examples
- *
- * Produces sequence of numbers
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate(0, x => x < 3, x => x + 1, x => x);
- *
- * result.subscribe(x => console.log(x));
- *
- * // Logs:
- * // 0
- * // 1
- * // 2
- * ```
- *
- * Use `asapScheduler`
- *
- * ```ts
- * import { generate, asapScheduler } from 'rxjs';
- *
- * const result = generate(1, x => x < 5, x => x * 2, x => x + 1, asapScheduler);
- *
- * result.subscribe(x => console.log(x));
- *
- * // Logs:
- * // 2
- * // 3
- * // 5
- * ```
- *
- * @see {@link from}
- * @see {@link Observable}
- *
- * @param initialState Initial state.
- * @param condition Condition to terminate generation (upon returning false).
- * @param iterate Iteration step function.
- * @param resultSelector Selector function for results produced in the sequence.
- * @param scheduler A {@link SchedulerLike} on which to run the generator loop.
- * If not provided, defaults to emit immediately.
- * @returns The generated sequence.
- * @deprecated Instead of passing separate arguments, use the options argument.
- * Signatures taking separate arguments will be removed in v8.
- */
- export function generate<T, S>(
- initialState: S,
- condition: ConditionFunc<S>,
- iterate: IterateFunc<S>,
- resultSelector: ResultFunc<S, T>,
- scheduler?: SchedulerLike
- ): Observable<T>;
- /**
- * Generates an Observable by running a state-driven loop
- * that emits an element on each iteration.
- *
- * <span class="informal">Use it instead of nexting values in a for loop.</span>
- *
- * 
- *
- * `generate` allows you to create a stream of values generated with a loop very similar to
- * a traditional for loop. The first argument of `generate` is a beginning value. The second argument
- * is a function that accepts this value and tests if some condition still holds. If it does,
- * then the loop continues, if not, it stops. The third value is a function which takes the
- * previously defined value and modifies it in some way on each iteration. Note how these three parameters
- * are direct equivalents of three expressions in a traditional for loop: the first expression
- * initializes some state (for example, a numeric index), the second tests if the loop can perform the next
- * iteration (for example, if the index is lower than 10) and the third states how the defined value
- * will be modified on every step (for example, the index will be incremented by one).
- *
- * Return value of a `generate` operator is an Observable that on each loop iteration
- * emits a value. First of all, the condition function is ran. If it returns true, then the Observable
- * emits the currently stored value (initial value at the first iteration) and finally updates
- * that value with iterate function. If at some point the condition returns false, then the Observable
- * completes at that moment.
- *
- * Optionally you can pass a fourth parameter to `generate` - a result selector function which allows you
- * to immediately map the value that would normally be emitted by an Observable.
- *
- * If you find three anonymous functions in `generate` call hard to read, you can provide
- * a single object to the operator instead where the object has the properties: `initialState`,
- * `condition`, `iterate` and `resultSelector`, which should have respective values that you
- * would normally pass to `generate`. `resultSelector` is still optional, but that form
- * of calling `generate` allows you to omit `condition` as well. If you omit it, that means
- * condition always holds, or in other words the resulting Observable will never complete.
- *
- * Both forms of `generate` can optionally accept a scheduler. In case of a multi-parameter call,
- * scheduler simply comes as a last argument (no matter if there is a `resultSelector`
- * function or not). In case of a single-parameter call, you can provide it as a
- * `scheduler` property on the object passed to the operator. In both cases, a scheduler decides when
- * the next iteration of the loop will happen and therefore when the next value will be emitted
- * by the Observable. For example, to ensure that each value is pushed to the Observer
- * on a separate task in the event loop, you could use the `async` scheduler. Note that
- * by default (when no scheduler is passed) values are simply emitted synchronously.
- *
- *
- * ## Examples
- *
- * Use with condition and iterate functions
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate(0, x => x < 3, x => x + 1);
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!')
- * });
- *
- * // Logs:
- * // 0
- * // 1
- * // 2
- * // 'Complete!'
- * ```
- *
- * Use with condition, iterate and resultSelector functions
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate(0, x => x < 3, x => x + 1, x => x * 1000);
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!')
- * });
- *
- * // Logs:
- * // 0
- * // 1000
- * // 2000
- * // 'Complete!'
- * ```
- *
- * Use with options object
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate({
- * initialState: 0,
- * condition(value) { return value < 3; },
- * iterate(value) { return value + 1; },
- * resultSelector(value) { return value * 1000; }
- * });
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!')
- * });
- *
- * // Logs:
- * // 0
- * // 1000
- * // 2000
- * // 'Complete!'
- * ```
- *
- * Use options object without condition function
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate({
- * initialState: 0,
- * iterate(value) { return value + 1; },
- * resultSelector(value) { return value * 1000; }
- * });
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!') // This will never run
- * });
- *
- * // Logs:
- * // 0
- * // 1000
- * // 2000
- * // 3000
- * // ...and never stops.
- * ```
- *
- * @see {@link from}
- *
- * @param initialState Initial state.
- * @param condition Condition to terminate generation (upon returning false).
- * @param iterate Iteration step function.
- * @param scheduler A {@link Scheduler} on which to run the generator loop. If not
- * provided, defaults to emitting immediately.
- * @return The generated sequence.
- * @deprecated Instead of passing separate arguments, use the options argument.
- * Signatures taking separate arguments will be removed in v8.
- */
- export function generate<S>(
- initialState: S,
- condition: ConditionFunc<S>,
- iterate: IterateFunc<S>,
- scheduler?: SchedulerLike
- ): Observable<S>;
- /**
- * Generates an observable sequence by running a state-driven loop
- * producing the sequence's elements, using the specified scheduler
- * to send out observer messages.
- * The overload accepts options object that might contain initial state, iterate,
- * condition and scheduler.
- *
- * 
- *
- * ## Examples
- *
- * Use options object with condition function
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate({
- * initialState: 0,
- * condition: x => x < 3,
- * iterate: x => x + 1
- * });
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!')
- * });
- *
- * // Logs:
- * // 0
- * // 1
- * // 2
- * // 'Complete!'
- * ```
- *
- * @see {@link from}
- * @see {@link Observable}
- *
- * @param options Object that must contain initialState, iterate and might contain condition and scheduler.
- * @returns The generated sequence.
- */
- export function generate<S>(options: GenerateBaseOptions<S>): Observable<S>;
- /**
- * Generates an observable sequence by running a state-driven loop
- * producing the sequence's elements, using the specified scheduler
- * to send out observer messages.
- * The overload accepts options object that might contain initial state, iterate,
- * condition, result selector and scheduler.
- *
- * 
- *
- * ## Examples
- *
- * Use options object with condition and iterate function
- *
- * ```ts
- * import { generate } from 'rxjs';
- *
- * const result = generate({
- * initialState: 0,
- * condition: x => x < 3,
- * iterate: x => x + 1,
- * resultSelector: x => x
- * });
- *
- * result.subscribe({
- * next: value => console.log(value),
- * complete: () => console.log('Complete!')
- * });
- *
- * // Logs:
- * // 0
- * // 1
- * // 2
- * // 'Complete!'
- * ```
- *
- * @see {@link from}
- * @see {@link Observable}
- *
- * @param options Object that must contain initialState, iterate, resultSelector and might contain condition and scheduler.
- * @returns The generated sequence.
- */
- export function generate<T, S>(options: GenerateOptions<T, S>): Observable<T>;
- export function generate<T, S>(
- initialStateOrOptions: S | GenerateOptions<T, S>,
- condition?: ConditionFunc<S>,
- iterate?: IterateFunc<S>,
- resultSelectorOrScheduler?: ResultFunc<S, T> | SchedulerLike,
- scheduler?: SchedulerLike
- ): Observable<T> {
- let resultSelector: ResultFunc<S, T>;
- let initialState: S;
- // TODO: Remove this as we move away from deprecated signatures
- // and move towards a configuration object argument.
- if (arguments.length === 1) {
- // If we only have one argument, we can assume it is a configuration object.
- // Note that folks not using TypeScript may trip over this.
- ({
- initialState,
- condition,
- iterate,
- resultSelector = identity as ResultFunc<S, T>,
- scheduler,
- } = initialStateOrOptions as GenerateOptions<T, S>);
- } else {
- // Deprecated arguments path. Figure out what the user
- // passed and set it here.
- initialState = initialStateOrOptions as S;
- if (!resultSelectorOrScheduler || isScheduler(resultSelectorOrScheduler)) {
- resultSelector = identity as ResultFunc<S, T>;
- scheduler = resultSelectorOrScheduler as SchedulerLike;
- } else {
- resultSelector = resultSelectorOrScheduler as ResultFunc<S, T>;
- }
- }
- // The actual generator used to "generate" values.
- function* gen() {
- for (let state = initialState; !condition || condition(state); state = iterate!(state)) {
- yield resultSelector(state);
- }
- }
- // We use `defer` because we want to defer the creation of the iterator from the iterable.
- return defer(
- (scheduler
- ? // If a scheduler was provided, use `scheduleIterable` to ensure that iteration/generation
- // happens on the scheduler.
- () => scheduleIterable(gen(), scheduler!)
- : // Otherwise, if there's no scheduler, we can just use the generator function directly in
- // `defer` and executing it will return the generator (which is iterable).
- gen) as () => ObservableInput<T>
- );
- }
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