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assertionFailure(_:file:line:)

Indicates that an internal consistency check failed.

Declaration

func assertionFailure(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line)

Parameters

  • message:

    A string to print in a playground or -Onone build. The default is an empty string.

  • file:

    The file name to print with message. The default is the file where assertionFailure(_:file:line:) is called.

  • line:

    The line number to print along with message. The default is the line number where assertionFailure(_:file:line:) is called.

Discussion

This function’s effect varies depending on the build flag used:

  • In playgrounds and -Onone builds (the default for Xcode’s Debug configuration), stop program execution in a debuggable state after printing message.

  • In -O builds, has no effect.

  • In -Ounchecked builds, the optimizer may assume that this function is never called. Failure to satisfy that assumption is a serious programming error.

See Also

Testing