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Sharpshooter: debugging for lazy people

Paul Hudson       @twostraws

There are lots of ways of debugging programs, but probably the first one we all learn is writing print() statements everywhere in our code. This simple approach makes it easy to follow program flow: functionA() got called first, then functionB(), then evilCrashFunction(), and boom – you've found what causes the problem.

Despite this approach being primitive at best, it tends to stick simply because it was the first thing we learned, so even experienced developers have been known to scatter some print() calls around to figure out what's going on.

Well, if this is your preferred approach – or if you know a "friend" who works like this – I wrote a new Xcode extension that will help. It's called Sharpshooter, and it lets you add or remove print() statements to your function entry points in just one click.

Here’s an example of code before adding comments:

class BrokenStuff {
    func broken() {
        print("<Silent screaming>")
    }

    private func reallyBroken() {
        print("<Tears>")
    }

    static private func superBroken() {
        print("<Silent screaming *and* tears>")
    }
}

And after:

class BrokenStuff {
    func broken() {
        print("# Sharpshooter: Entering broken()")
        print("<Silent screaming>")
    }

    private func reallyBroken() {
        print("# Sharpshooter: Entering reallyBroken()")
        print("<Tears>")
    }

    static private func superBroken() {
        print("# Sharpshooter: Entering superBroken()")
        print("<Silent screaming and tears>")
    }
}

In case you were wondering, the name comes from a joke about a Texan sharpshooter who fires gunshots at the door of a barn, then draws a target around the biggest cluster of hits and claims to be a sharpshooter – a pretty accurate analogy for finding bugs using print(), I think.

Link: Sharpshooter.

 

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About the author

Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and Mario Kart world champion. OK, so that last part isn't true. If you're curious you can learn more here.

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