I just notice Swift has this function, which could stop the project when condition is failed.

assert(::file:line:)

Let’s check its documentation.

Performs a traditional C-style assert with an optional message.

OK. From this description, we might still confused what its saying.

In the bottom discussion part, Apple explained for us:

Use this function for internal sanity checks that are active during testing but do not impact performance of shipping code. To check for invalid usage in Release builds, see precondition(::file:line:).

So actually it will only showed under Debug build, which not have influence on our Real build. If we also want to show it on Real build, we could use precondition(_:_:file:line:)

Also under this discussion, Apple listed all bild types:

• In playgrounds and -Onone builds (the default for Xcode’s Debug configuration): If condition evaluates to false, stop program execution in a debuggable state after printing message.
• In -O builds (the default for Xcode’s Release configuration), condition is not evaluated, and there are no effects.
• In -Ounchecked builds, condition is not evaluated, but the optimizer may assume that it always evaluates to true. Failure to satisfy that assumption is a serious programming error.

And we could see assert(_:_:file:line) condition part is said it will only evaluated in playgroud and -Onone builds.

And -Onone builds is: default for Xcode’s Debug configuation

So we could use it safely in our code

Reference

https://developer.apple.com/documentation/swift/1541112-assert