Branch

A branch expression starts a block of one or more async subexpressions, and any expression that follows after is executed immediately, without waiting for the branch expressions to complete.

You can use branch essentially to treat any async block of code as though it were fire-and-forget immediate, but it still must be called within an async context.

branch:
    # This block continues until completed
    AsyncFunction1()    # Starts effectively the same time as AsyncFunction3()
    Method1()  # Block can be mixed with immediate expressions
    AsyncFunction2()
AsyncFunction3()  # Starts effectively the same time as AsyncFunction1()
# If branch block task is still running when AsyncFunction3 completes
# then any remaining branch task is canceled
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branch: # This block continues until completed AsyncFunction1() # Starts effectively the same time as AsyncFunction3() Method1() # Block can be mixed with immediate expressions AsyncFunction2() AsyncFunction3() # Starts effectively the same time as AsyncFunction1() # If branch block task is still running when AsyncFunction3 completes # then any remaining branch task is canceled

The following code shows the syntax for the branch expression.

expression0
branch:
    slow-expression
    mid-expression
    fast-expression
expression1
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expression0 branch: slow-expression mid-expression fast-expression expression1

The diagram below shows the execution flow of the expressions.

It is similar to the unstructured concurrency spawn expression, but branch allows for any arbitrary block of code, and is only permissible within, and bounded by, an enclosing async context. Because of this, branch is preferred over spawn whenever possible.

Branch Expression Use

A branch expression may not currently be used in the body of an iteration expression such as loop or for. If it must be used then wrap it in an async function and have the iteration expression call that function.