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Promise Since 1.0.0 ​

Promises are a way to handle asynchronous code in a synchronous manner. They are similar to the Promise class in JavaScript. This documentation assumes you already have a basic understanding of promises.

Functions ​

new Since 1.0.0 ​

Creates a new promise.

lua
(
	Callback: (Resolve: (...any) -> (), Reject: (...any) -> ()) -> (),
) -> Promise

This function immediately calls the callback in a new thread with two functions, Resolve and Reject. These functions are used, as their names imply, to resolve or reject the promise.

TIP

You can pass multiple values to Resolve and Reject.

WARNING

Resolve and reject can only be called once. On the next execution step after either of these functions are called, the promise thread will be closed.

lua
Promise.new(function(Resolve, Reject)
	Resolve("Hello, world!")
end)

Resolve Since 1.0.0 ​

Creates a new promise that is already resolved.

lua
(...any) -> Promise

This function creates a new promise that is already resolved with the values passed to it.

TIP

Use this function for synchronous code, it's about 10x faster than Promise.new.

lua
Promise.Resolve("Hello, world!")

Reject Since 1.0.0 ​

Creates a new promise that is already rejected.

lua
(...any) -> Promise

This function creates a new promise that is already rejected with the values passed to it.

TIP

Use this function for synchronous code, it's about 10x faster than Promise.new.

lua
Promise.Reject("Hello, world!")

Methods ​

Then Since 1.0.0 ​

Chains from a promise to another promise.

lua
(
	OnResolve: ((...any) -> (...any))?,
	OnReject: ((...any) -> (...any))?,
) -> Promise

This function returns a new promise that is resolved or rejected based on the return value of the callback functions. This should exactly match the A+ Spec.

lua
Promise.new(function(Resolve, Reject)
	Resolve("Hello, world!")
end):Then(function(Value)
	print(Value) -- Hello, world!
end)

Catch Since 1.0.0 ​

Chains from a promise to another promise, but only if the promise is rejected.

lua
(
	OnReject: ((...any) -> (...any))?,
) -> Promise

This function is the equivalent of Promise:Then(nil, OnReject).

lua
Promise.new(function(Resolve, Reject)
	Reject("Hello, world!")
end):Catch(function(Value)
	print(Value) -- Hello, world!
end)

Finally Since 1.0.0 ​

Chains from a promise to another promise, but is always called.

lua
(
	OnFinally: ((...any) -> (...any))?,
) -> Promise

This function is the equivalent of Promise:Then(OnFinally, OnFinally).

lua
Promise.new(function(Resolve, Reject)
	Resolve("Hello, world!")
end):Finally(function(Value)
	print(Value) -- Hello, world!
end)

Await Yields Since 1.0.0 ​

Waits for a promise to resolve or reject.

lua
() -> (...any)

This function will wait for the promise to resolve or reject. If the promise is resolved, the values passed to Resolve will be returned. If the promise is rejected, the call will error with the first rejection value.

lua
Promise.new(function(Resolve, Reject)
	Resolve("Hello, world!")
end):Await() -- Hello, world!