Spawn in Verse | Fortnite Documentation | Epic Developer Community

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The spawn expression starts one async function invocation, and any expression that follows the spawn is executed immediately while the started async function task continues independently until it completes.

Verse

# Continues until completed without blocking
spawn{AsyncFunction1()}  # Started at same time as expression0
expression0         # Started at same time as AsyncFunction1()

# Continues until completed without blocking
spawn{AsyncFunction1()}  # Started at same time as expression0
expression0         # Started at same time as AsyncFunction1()

The following code shows the syntax for the spawn expression.

Verse

expression0
spawn{ expression1 }
expression2

expression0
spawn{ expression1 }
expression2

The diagram below shows the execution flow of the expressions.

Diagram showing the execution flow of the spawn expression

While similar to branch, the spawn body is limited to a single async function call. It is also allowed outside of an async context, so it can be called within both non-async and async functions.

A spawn expression should be treated like an emergency escape hatch, while branch should be used in place of spawn whenever possible.

Spawn Expression Use


Where you can use a `spawn` expression	Any context.
Invocation time of the `spawn` expression	Immediate.
Requirements for `spawn` code block	The body of the `spawn` expression is started as soon as it is encountered. It must have at least one async expression.
What the `spawn` expression does	The body of a `spawn` creates an async context like the body of an async function. However, only a single async function call is allowed within the `spawn` body. The async function of the `spawn` is started as soon as it is encountered, and evaluates as much as possible until it encounters something suspending or blocking. The spawned async function continues to evaluate until it completes without any further connection to the location where it was spawned.
When the `spawn` expression completes	The `spawn` expression completes immediately.
When the next expression after `spawn` starts	Any next expression that follows the `spawn` expression is started immediately.
Result of the `spawn` expression	A `spawn` has a task result.