Category Archives: Swift

how to quickly toggle Swift Compiler warnings

I thought I’d share this little AppleScript for anyone working with Xcode 8.3.3 and using Swift.

One of the things I find intrusive are the constant Swift Compiler warnings while I’m actually in the middle of writing a block of code (e.g, ‘…value was never used consider replacing…’). Well, yeah, it’s not been used *yet* …grrr!

However, turning off compiler warnings isn’t something I want to do either. It’s too easy to go into the build settings, turn them off, do a bit of coding, take a break, do a bit more coding…oh, three thousand lines later and I suddenly realize why Xcode hasn’t been correcting my mistakes all afternoon!

This script allows you to quickly and easily toggle the warnings from a hotkey, and just gives you a gentle reminder as to what you’ve done. Of course that won’t stop you forgetting, but assigning a hotkey for this script makes it painless to just turn warnings off and back on again as soon as you’ve got past whatever bit of code the compiler was complaining about.

Xcode unfortunately doesn’t have its own scripts menu, so in order to assign the script a hotkey, you’ll need to either make it into a Service with Automator or use a script runner like Red Sweater’s FastScripts.

on sendNotification(aVal)

display notification "Suppress Warnings was set to " & aVal with title "Swift Compiler - Warnings Policies"

end sendNotification

tell application id ""
tell its front document
tell its front project
tell its front target
tell its build configuration "Debug"
set b to build setting "SWIFT_SUPPRESS_WARNINGS"
if b's value is "NO" then
set b's value to "YES"
set b's value to "NO"
end if
my sendNotification(b's value)
end tell
end tell
end tell
end tell
end tell

If copying the code above doesn’t build, get the raw source from my pastebin here. Here’s how it looks in Script Debugger 6:

Enjoy! 🙂

how to create a bootable macOS installer

If you are preparing to install macOS on multiple computers, one of the things that can make your life simpler (and the waiting shorter) is a bootable USB installer.

The idea of the installer is that you only need to download the macOS from the App Store once. Usually, when you run the installer after downloading it, it’ll delete itself and you have to go through the whole download process again on each machine or disk that you want to install macOS onto. By making a bootable USB drive, you simply plug the drive in to your mac, launch the installer app and tell it where to install the OS. You can repeat this as many times as you like as the installer will remain safe on your USB.

There are various ways to make a bootable USB installer, but they all involve the same process:

1. Download the macOS Installer from the App Store.
2. Run the createinstallmedia command from the Terminal, an AppleScript or a helper app.
3. Reboot your mac, choosing the newly created USB as the startup disk.
4. Run the from the USB.

Step 2 is where the fun is. The createinstallmedia command can be tricky to get right, particularly if you’re not familiar with working on the command line. For those of you that are, follow Apple’s instructions here.

For a little more convenience, I wrapped all that inside an AppleScript which will first ask you for the location of the installer, then ask you to choose the USB target.

For maximum convenience, I also wrote a free little Swift app I’ve dubbed ‘Boot Buddy‘ (cos “Create bootable macOS Installer” just didn’t quite have the right ring to it..!) that will present the whole thing in a neat little user interface. Three clicks, more or less, and you’re done.

Boot Buddy doesn’t require an admin password to install, but you do need to provide an admin password to actually create the bootable installer as the createinstallmedia process has to be run as root. Boot Buddy doesn’t see or use this in any way whatsoever other than to start the createinstallmedia process or to cancel it (if you choose to do so); authorisation is handed off to macOS to take care of.

Boot Buddy requires macOS 10.11 or higher and can create bootable USBs from Mavericks, Yosemite, El Capitan, Sierra and High Sierra installer apps.

Share and enjoy! 🙂

UITableView doesn’t immediately reload data

Here’s a little problem and solution I ran into the other day while using UITableView. I wanted to have a master-detail set up in which the UITableView was segued to after an initial home screen.

The problem occurred whenever I added or deleted something in the UITableView, segued back to the home page and then returned to the table view. Sometimes the table would not update. Going out and back into the view a second time, however, would finally reload my data and show me the changes. Why was my app needing to load the view twice before the table would show any changes?

Logging showed me that something even weirder was going on: Every time I segued into the table view, the viewDidLoad method was being called not once, but twice. So basically, to get my updated data to show, I was actually calling viewDidLoad four times!

I worked through a whole bunch of stackexchange posts related to various problems and solutions with the reloadData method — adding delays, removing it from any edit- or insert- methods and so on, calling it on the main thread — but the problem stubbornly remained.

Then I noticed something else. In my awakeFromNib method, the call to super had somehow got pushed to the end of the method, after a bunch of other set up calls. I’m not sure how it got there, but I did remember seeing a WWDC 2014 Swift video pointing out that one difference between Objective-C and Swift was that calls to super need to be made after doing any initial set up in Swift’s case, but before for Objective-C. Since this was an Obj-C project, what was my call to super doing at the end of the method?

And as if by magic, moving [super awakeFromNib] to the beginning of my awakeFromNib method resulted in viewDidLoad only being called once, and my table view updating correctly.

Though I found quite a few threads with people having a similar problem with UITableView’s needing two calls before updating, I haven’t come across this particular solution to (or cause of) the problem. Hopefully, this post will save someone else a few hours of head scratching!

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