Logging for beginners in Swift

Fundamental output in Swift utilizing print

The very first technique I might like to point out you is the print function. It will possibly write the textual illustration of the given gadgets to the usual output. In different phrases we are able to merely say that it will possibly print textual content to the display screen. Many of the hello word programs make the most of this technique to show the well-known “Good day world!” message. In Swift, print is kind of a robust technique, since you possibly can cross round a number of gadgets for printing out plus you possibly can specify a separator string and a terminator parameter. 🤔

print("Good day World!")

The snippet above will show the Good day World! textual content adopted by a newline character (n), it’s because the default terminator is at all times a newline. You may override this conduct by offering your personal terminator string.

print("Good day World!", terminator: "")

For those who run this instance utilizing Xcode it’s best to see that the “Program ended with exit code: 0” textual content will seem in a newline within the first case, however within the second state of affairs it will be printed out proper after the “Good day World!” sentence. For those who run this system utilizing a Terminal utility, a % character be current as a substitute of the brand new line within the second case. 💡

What about printing out a number of variables? It’s doable to present a number of gadgets to the print perform, they are often actually something, print can deal with strings, integers and every kind of different variables. Print below the hood will convert the variable into a correct string illustration, so you do not have to fiddle with sort casting on a regular basis, however merely print out something.

print(1, 2, 3, 4, 5)


print(1, "two", 3.14, true)

You may also customise the separator character by means of an argument. So if you happen to want a coma character (adopted by an area) in between the weather, you possibly can write one thing like this:

print("a", "b", "c", separator: ", ")

Effectively, in my previous article you’ve gotten seen learn how to assemble numerous strings utilizing literals and interpolation, you need to use all these variables to print out stuff to the console.

print("""
            __
           / _)
    .-^^^-/ /
 __/       /
<__.|_|-|_|
""")

For instance, this is a cute multi-line ascii artwork dinosaur. 🦕

Debugging and print

Generally it could be cool to know just a bit bit of additional information in regards to the printed variable, that is when debugPrint may also help you. The principle distinction between print and debugPrint is that whereas print merely converts all the things to string, debug print provides you with a short debug information in regards to the given gadgets. The debugPrint technique will print out numbers similar to print does, it will add double quotes round strings, and it will print some additional information about many of the different “complicated” varieties.

print(1) 
debugPrint(1) 

print("foo") 
debugPrint("foo") 

print(1...5) 
debugPrint(1...5) 

Actually I’ve nearly by no means used this technique, and I at all times most well-liked print if I needed to print out one thing to the console, nevertheless it’s at all times good to know that there’s such an possibility accessible built-in to the usual library, nevertheless there’s a technique that can provide you far more information… 🧐

Debugging utilizing dump

The dump method can print out the given object’s content material utilizing its mirror to the usual output. Lengthy story brief, this perform will present you a extra detailed view in regards to the property. For scalar values the dump technique will produce nearly the identical output as debug-print, besides the dump line at all times begins with a touch character, however for extra complicated varieties it will output the underlying construction of the item. Don’t be concerned, you need not perceive the output of this technique, simply keep in mind that it will possibly present you useful information throughout debugging. 🐞

dump(1)
dump(3.14)
dump("foo")
dump(1...5)

The ClosedRange struct is a built-in sort with a lowerBound and an upperBound property. Whereas the print perform solely returned the outlined vary (1…5), the debugPrint technique additionally revealed the kind of the item, dump takes this one step additional by exhibiting us the precise decrease and higher certain properties of the worth. This may be extraordinarily useful when you’ve gotten a fancy sort with a number of underlying properties that you simply need to rapidly examine for some cause. 🔍

By the best way, debugging is the act of discovering (and resolving) bugs. Bugs are issues in your program code that stop regular operation. Builders can use debugger tools to run and examine code step-by-step, line by line or per instruction, however most of them are merely placing print statements into the code to see the present state or results of a given perform. 🤷‍♂️

Dump has just a few extra perform arguments that you may configure:

dump("take a look at", title: "my-variable", indent: 4, maxDepth: 5, maxItems: 5)

You can provide a reputation to every dumped variable, add some additional indentation earlier than the sprint character, specify the utmost depth for descendents and the utmost variety of parts for which to jot down the total contents. Be happy to play with these parameters for some time. 😉

As you possibly can see dump is kind of a robust technique, however nonetheless there are different capabilities for logging functions, let me present you one that’s coming from the Goal-C occasions.

NSLog – the legacy logger perform

In case you have ever labored with Goal-C you need to be conversant in the NS prefixes. The NSLog perform can log an error message to the Apple System Log facility console. It isn’t a part of the Swift standard library, however you need to import the Foundation framework as a way to use NSLog.

import Basis

NSLog("I am a dinosaur.")

It’s best to know that NSLog will print the present date & time first, then it will show the title of the working program with the method and thread identifiers and solely then it will print your message.

Simply to be clear, NSLog is coming from the Goal-C period, it isn’t a beneficial logging answer anymore. It’s also very gradual and that may trigger some points if you happen to want exactly timed outputs. That is why I do NOT recommend using NSLog in any respect, however you additionally need to know that till just a few years in the past there was no higher built-in various for it, I am not judging, simply saying… 😅

Unified Logging and Exercise Tracing

If you wish to ship log messages on an Apple machine to the unified logging system, you need to use the OSLog framework. This new software was launched at WWDC 2016 and not too long ago obtained some good API refinements & updates. It’s best to positively test the OSLog and Unified Logging recommended by Apple article if you wish to be taught extra about this matter it is an ideal write up.

My solely concern about this logging API is that it isn’t that common. It really works nice on Apple platforms, however since Swift is an common language if you wish to add Linux and even Home windows assist, this answer will not be just right for you…

SwiftLog – A Logging API package deal for Swift

This open source package might be simply built-in into your Swift initiatives through the Swift Package Manager. You simply need to set it up as a dependency within the Package deal.swift manifest file or you possibly can hook it utilizing Xcode below the File > Swift Packages menu as an SPM dependency.

import PackageDescription

let package deal = Package deal(
    title: "myProject",
    dependencies: [
        .package(url: "https://github.com/apple/swift-log.git", from: "1.4.0"),
    ],
    targets: [
        .target(name: "myProject", dependencies: [
            .product(name: "Logging", package: "swift-log")
        ])
    ]
)

The utilization is de facto simple. First you need to import the Logging framework, then you definately create a logger and you utilize that logger occasion to print out numerous log messages.

import Logging

let logger = Logger(label: "app-identifier")

logger.information("Good day World!")

The next log ranges are supported:

• hint

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• debug
• information
• discover
• warning
• error
• vital

You may also connect further logging metadata to the logger, it’s best to test the readme for more information about this feature. SwiftLog is utilized in many real-world initiatives, corresponding to Vapor 4 (a server facet Swift framework), this additionally implies that it really works nice on Linux working programs. 🐧

Conclusion

If it involves logging, there are a number of good choices to select from. It solely will depend on your wants which one is the very best, however basically we are able to say that it’s time to go away behind NSLog, and time to make use of the brand new OSLog framework. In case you are utilizing Swift on non-Apple platform it’s best to think about using the SwiftLog library, which can be supplied by Apple.

Alternatively in case you are simply scratching the floor and you do not want that many choices or log ranges you possibly can merely keep on with print and dump statements. It is completely high quality to debug utilizing these easy methods at first. Mastering one thing takes time and debuggers might be fairly scary at first sight. Use print as a lot as you want, however at all times attempt to enhance your instruments & information over time, I hope this text offers you a greater view of the accessible logging instruments. 🤓