Mac Developer Tip: Programmatically Starting a Search on the Mac App Store

Working on Transloader 3, I wanted to re-implement the Finder’s Open With… contextual menu:

The Finder's Open With contextual menu

Getting the apps in there turned out to be the easy part. What took some effort was the “App Store…” menu item, as I wanted to precisely replicate its functionality.

Transloader 3's Open With contextual menu

Right-click a file in Finder, select Open With -> App Store…, and it will launch the Mac App Store with a UTI search, for example: uti:public.zip-archive.
This will give you a list of all apps available in the Mac App Store that can handle that file type. Neat!

The ‘macappstores’ URL scheme

The Mac App Store app luckily offers a URL scheme:

  • macappstores://
    Launches the Mac App Store
  • macappstores://showUpdatesPage
    Launches the Mac App Store and takes you directly to your Updates page
  • macappstores://showPurchasesPage
    Launches the Mac App Store and takes you directly to your Purchased page
  • macappstores://itunes.apple.com/app/idYOURAPPID
    Launches the Mac App Store and takes you directly to the product page, identified by the product ID

That’s very practical, but not what I was looking for. I was in need of a way to start a search the way Finder does.

In order to find out the URL Finder uses, I wrote a quick throwaway-app that would overtake the Mac App Store’s URL schemes (using LSSetDefaultHandlerForURLScheme) and print out the URL that was opened.
Alas – no dice. Apparently, Finder uses Apple Events or some other magic that “can not be used in a third-party sandboxed app anyway”™ to do its bidding.

After googling the issue, I found a URL that supposedly worked: macappstores://ax.search.itunes.apple.com/WebObjects/MZSearch.woa/wa/search?q=searchterm, but just to pour more salt into an already wide-open wound, it only worked on pre-10.9 systems:

The search URL in 10.9-and-beyond systems

Another dead end. Or was it?
I guess I should have experimented with that URL a little, because Jan Vitturi (@jan4843 on twitter) had the answer: just remove “ax.” from the URL, and it works (on both pre-10.9 and post-10.9 systems)!

Using this URL:
macappstores://search.itunes.apple.com/WebObjects/MZSearch.woa/wa/search?q=searchterm
I was able to get a search going on the Mac App Store, right from within my app.

Sadly, there’s a caveat.
I can’t do a UTI search this way. When I pass (even a percent-escaped) search term along the lines of ‘uti:public.zip-archive’, the Mac App Store tells me there are no results. Reloading that very same page then does show the results – weird and annoying, but nothing I was able to work around.
Using extension:zip seemed to work a little better, but still didn’t return all results a reload would.

Jan Vitturi to the rescue again – the URL’s a little different for UTI or extension searches:
macappstores://search.itunes.apple.com/WebObjects/MZSearch.woa/wa/docTypeLookup?uti=youruti

Alternatively, instead of uti=…, you can use extension=… to search by file path extensions.

My sincere thanks go to Jan Vitturi!

 

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Mac Developer Tip: NSTouchBar in a Share Extension

You’re working on your Share extension with support for MacBook Pro’s Touch Bar, but it’s empty and doesn’t appear when your extension is loaded?

NSTouchBar Empty

The solution is simple:

Solution for showing NSTouchBar from within a Share extension

Call [self.view.window makeFirstResponder:self.view]; and it will push your glorious NSTouchBar onto the stack:

NSTouchBar working in a Share extension

Hope it helps – it would have saved me 20 minutes if I’d known ;)

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Mac Developer Tip: How to Simulate Memory Pressure

In iOS Simulator, you can, via a menu item, quickly simulate memory pressure for the simulated device to see if your app behaves correctly under low memory conditions (releasing caches, cleaning up resources, and so on).

Recently, I had the need for it on the Mac (where such a menu item is not available), while working on an XPC service for Yoink, to see if it terminated properly under certain conditions.

Meet the memory_pressure tool

OS X comes with the Terminal, and with the Terminal come some awesome tools. Among them is memory_pressure. Its man page says it all:

Apply real or simulate memory pressure on the system.

Usage of memory_tool

sudo memory_pressure -S -l critical

What this does is simulate (-S) a memory pressure of a critical level (-l critical).
sudo is needed, otherwise it will probably fail with an “Operation not permitted” error.

memory_tool’s options

-l:   Two levels of pressure are supported: ‘warn’ and ‘critical’.
-p:  For real pressure, this lets you define how much memory should remain free, in percent of total memory.
-S:  Simulate memory pressure, don’t really allocate memory.
-s:   If applying real pressure, this is the duration to wait before allocating or freeing memory.
       If it’s simulated pressure, the system will be maintained at an artificial memory level for this duration.