dispatchPrecondition(condition:)

Checks a dispatch condition necessary for further execution.

Declaration

func dispatchPrecondition(condition: @autoclosure () -> DispatchPredicate)

Use this function to detect conditions about the current execution context that must prevent the program from proceeding even in shipping code.

In playgrounds and -Onone builds (the default for Xcode’s Debug configuration): if condition evaluates to false, stop program execution in a debuggable state.
In -O builds (the default for Xcode’s Release configuration): if condition evaluates to false, stop program execution.
In -Ounchecked builds, condition is not evaluated, but the optimizer may assume that it would evaluate to true. Failure to satisfy that assumption in -Ounchecked builds is a serious programming error.