Use this function to stop the program when control flow can only reach the
call if your API was improperly used. This function's effects vary
depending on the build flag used:
In playgrounds and -Onone builds (the default for Xcode's Debug
configuration), stops program execution in a debuggable state after
printing message.
In -O builds (the default for Xcode's Release configuration), stops
program execution.
In -Ounchecked builds, the optimizer may assume that this function is
never called. Failure to satisfy that assumption is a serious
programming error.
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 preconditionFailure(_:file:line:) is called.
line: The line number to print along with message. The default is the
line number where preconditionFailure(_:file:line:) is called.
Indicates that a precondition was violated.
Use this function to stop the program when control flow can only reach the call if your API was improperly used. This function's effects vary depending on the build flag used:
In playgrounds and
-Ononebuilds (the default for Xcode's Debug configuration), stops program execution in a debuggable state after printingmessage.In
-Obuilds (the default for Xcode's Release configuration), stops program execution.In
-Ouncheckedbuilds, the optimizer may assume that this function is never called. Failure to satisfy that assumption is a serious programming error.Parameters: message: A string to print in a playground or
-Ononebuild. The default is an empty string. file: The file name to print withmessage. The default is the file wherepreconditionFailure(_:file:line:)is called. line: The line number to print along withmessage. The default is the line number wherepreconditionFailure(_:file:line:)is called.Declaration
funcpreconditionFailure(_message: @autoclosure() ->String=default,file:StaticString= #file,line:UInt= #line) ->Never