Very short – if not the shortest – Swift logging library.

I'm just a lone dude making risky-dink iOS apps. I do not want or need a fancy logging library. Here is what I do not need:

• Colors.
• Multiple channels.
• Logging anywhere else other than standard output.
• File rotation.
• Complicated filters.
• Helper functions that save me from typing 10 extra characters.
• Verbosity.
• Levels.
• Formatters.
• Thread safety.
• Appenders.
• XML anything.
• Document Object Model hierarchies.
• Targets.
• Layouts.

I don't even need date and time information. That line prefix that NSLog kicks out? Too long! You know what I like column 1 of my log files to contain? The first character of my log message.

So just use print(), right? Well, the problem is, I throw all those print statements around, but I'm only debugging 1 or 2 entities at a time, and I don't want to look at all those print statements from 2 weeks ago confusing me while I debug something now.

So the only feature I need is categories. I specify a category when I write the call to my logging function along with a message. Somewhere central, I can turn on or off what categories get logged.

So my requirements are:

• Print the message I pass in.
• Unless I don't want that message printed right now.

So anyway, here is my fancy logging library.

struct L {
    // These are the only categories that will be logged. Adjust accordingly.
    private static let categories = ["Pilot"]
    
    typealias M = ((String) -> Void)
    static let c:[String : M] = {
        var tmp = [String : M]()
        for s in L.categories {
            tmp[s] = L.m
        }
        return tmp
    }()
    
    static func m(message:String) {
        print(message)
    }
}

And here is how you use it.

class Pilot {
    private let n = String(Pilot)
....
    L.c[n]?("radians = \(radians)")
....
    L.c["Err"]?("state was never set!")
}

class Location {
    private let c = String(Location)
....
    L.c[c]?("directionToLocation = \(directionToLocation)")
}

Because categories only has "Pilot", only the "radians" log line will get printed. I can chose to use the names of classes for the category or any string I want.

When I'm ready to push to the App Store, I can leave categories as "Err" to record any errors. As if I'll ever be able to talk a user through pulling and sending me their device console logs.