promesa.core

*loop-run-fn*

dynamic

all

(all promises)

Given an array of promises, return a promise that is fulfilled when all the items in the array are fulfilled.

Example:

(-> (all [(promise :first-promise) (promise :second-promise)] (then (fn first-result second-result)) (println (str first-result “, ” second-result)

Will print out :first-promise, :second-promise.

If at least one of the promises is rejected, the resulting promise will be rejected.

any

(any promises)(any promises default)

Given an array of promises, return a promise that is fulfilled when first one item in the array is fulfilled.

bind

(bind p f)(bind p f executor)

A convenient alias for then.

cancel!

(cancel! p)

Cancel the promise.

cancelled?

(cancelled? v)

Return true if v is a cancelled promise.

catch

(catch p f)(catch p pred-or-type f)

Executes f when the promise p is rejected. Returns a promise resolved with the return value of f function handler.

catch'

(catch' p f)(catch' p pred-or-type f)

Executes f when the promise p is rejected. Returns a promise resolved with the return value of f function handler.

chain

(chain p f)(chain p f & fs)

Chain variable number of computations to be executed serially. Analogous to then that accepts variable number of functions.

chain'

(chain' p f)(chain' p f & fs)

Chain variable number of computations to be executed serially. Unlike chain does not flattens the return value of each step (probably this is more performant than chain).

create

(create f)(create f executor)

Create a promise instance from a factory function. If an executor is provided, the factory will be executed in the provided executor.

A factory function looks like (fn [resolve reject] (resolve 1)).

deferred

(deferred)

Creates an empty promise instance.

deferred?

(deferred? v)

Return true if v is a promise instance (alias to promise?.

delay

(delay t)(delay t v)(delay t v scheduler)

Given a timeout in miliseconds and optional value, returns a promise that will fulfilled with provided value (or nil) after the time is reached.

do!

macro

(do! & exprs)

Execute potentially side effectful code and return a promise resolved to the last expression. Always awaiting the result of each expression.

done?

Returns true if promise p is already done.

err

A short alias for error function.

error

(error f p)(error f type p)

Same as catch but with parameters inverted.

extract

(extract p)

Returns the current promise value.

finally

(finally p f)(finally p f executor)

Attach a potentially side-effectful handler to promise that will be executed independently if promise is resolved or rejected.

Returns the original promise and the return value of f function is ignored.

future

macro

(future & body)

Analogous to clojure.core/future that returns a promise instance instead of the Future. Usefull for execute synchronous code in a separate thread (also works in cljs).

handle

(handle p f)(handle p f executor)

Executes f when the promise p is resolved or is rejected. Returns a promise resolved with the return value of f function.

let

macro

(let bindings & body)

A let alternative that always returns promise and waits for all the promises on the bindings.

loop

macro

(loop bindings & body)

map

(map f p)(map executor f p)

Chains a computation f (function) to be executed when the promise p is successfully resolved.

Unlike then this does not performs automatic promise flattening. This is designed to be used with ->>.

mapcat

(mapcat f p)(mapcat executor f p)

Chains a computation f (function) to be executed when the promise p is successfully resolved. always expecting that f returns a promise that will be automatically unwrapped.

This is just a stricter version of then with reversed arguments in the same way as map.

This is designed to be used with ->>.

pending?

(pending? p)

Returns true if promise p is stil pending.

plet

macro

(plet bindings & body)

A parallel let; executes all the bindings in parallel and when all bindings are resolved, executes the body.

promise

(promise v)(promise v executor)

The coerce based promise constructor. Creates a appropriate promise instance depending on the provided value.

If an executor is provided, it will be used to resolve this promise.

promise?

(promise? v)

Return true if v is a promise instance.

promisify

(promisify callable)

Given a function that accepts a callback as the last argument return other function that returns a promise. Callback is expected to take single parameter (result of a computation).

race

(race promises)

recur

macro

(recur & args)

reject!

(reject! p e)

Reject a completable promise with an error.

rejected

(rejected v)

Return a rejected promise with provided reason.

rejected?

(rejected? p)

Returns true if promise p is already rejected.

resolve!

(resolve! o)(resolve! o v)

Resolve a completable promise with a value.

resolved

(resolved v)

Return a resolved promise with provided value.

resolved?

(resolved? p)

Returns true if promise p is already fulfilled.

run!

(run! f coll)(run! f coll executor)

A promise aware run! function.

then

(then p f)(then p f executor)

Chains a computation f (function) to be executed when the promise p is successfully resolved.

The computation will be executed in the calling thread by default; you also can provide a custom executor.

If the function f returns a promise instance, it will be automatically unwrapped.

then'

(then' p f)(then' p f executor)

Chains a computation f (function) to be executed when the promise p is successfully resolved.

The computation will be executed in the calling thread by default; you also can provide a custom executor.

Don’t perform flatten on the result.

timeout

(timeout p t)(timeout p t v)(timeout p t v scheduler)

Returns a cancellable promise that will be fulfilled with this promise’s fulfillment value or rejection reason. However, if this promise is not fulfilled or rejected within ms milliseconds, the returned promise is cancelled with a TimeoutError

wrap

(wrap v)