https://www.macrumors.com/2017/06/06/apple-to-phase-out-32-bit-mac-apps/
Yup, starting Jan 2018, Apple will only accept 64-Bit apps when you add a brand new application to the App Store. You can still update 32-Bit applications until June 2018. After that, if it ain’t 64-Bit it ain’t getting in.
They’ve also said that there will be compromises trying to run 32-Bit apps on the NEXT macOS (10.14), take this to mean that it’s going to be very detrimental to your customers experience with your software.
I’ve been expecting this change for the last few years now, especially after I was reporting some bugs in 32-Bit frameworks and an Apple engineer told me that anything other than 64-Bit Cocoa was unofficially deprecated.
First up; get your self a spare HDD and install High Sierra on it. Make sure that your apps work in High Sierra, you have 4 months till High Sierra goes public.
Next set about making sure your apps are 64-Bit, remember to use Feedback to submit any bugs you find in the 64-Bit framework. Consider that we only have 7 months to get 64-Bit working. 12 months if you don’t intend to create any new applications and 16 months if you don’t care about the Mac App Store.
Good luck to us all.
Well, looks like later this year Xojo will have 64-bit finalized and we will have to check all apps and rebuild as 64-bit.
Not a big worry.
Lucky, unlike Windows, 64 bit Mac is ready. Should not be terribly difficult to recompile. At least if the project is not crammed with old style declares…
Incidentally, that is where buying plugins makes life a whole lot easier 
The main problem will be users “stuck” on previous versions of xojo due to bugs, features or whatever. There will either be more sales of new versions of xojo or less apps out there.
Unfortunately I’ve made extensive use of MacOSLib in my app, and that’s 32-bit. I’m hoping that the upcoming Interops will make converting to 64-bit easier. Or else convert to MBS. Either will be a big job.
macOSLib IS open sourced and hosted where anyone could contribute to making it 64 bit
would seem a good community effort to undertake as I’m sure there are a lot of people who have used it
Unfortunately it’s an extremely complicated and inter-dependent set of classes. As you know, Charles Yeomans started the project and was the principle contributor. He posted on this forum some time ago that he’d cleaned it up and converted it to 64-bit, but after that he disappeared. It’s beyond my capabilities to convert it myself, and although I’ve offered to do some monkey work if guided, there isn’t much enthusiasm among the community. Do you think Interops would make creating replacements for certain MacOSLib classes easier?
That is where using declares as cooking recipes, meaning without understanding them, comes back to byte. Sure, using declares seems easier and faster than pure Xojo code, but there is a price to pay. Actually the price is simply to learn how to read the Apple Developer Library, see which parameters are needed, and make sure the corresponding datatype is used in the declare. In other words, understand the cooking ingredients.
The alternative is plugins. Contrary to voluntary efforts, plugins are maintained by the author, and for instance MBS insures a smooth transition. Christian Schmitz or Björg Eiríksson are outstanding professionals, and have updated their plugins as soon as 64 bit was available. I see all too often ‘no plugins, please’. As a friend of mine used to say “there are economies that end up costing a lot”.
[quote=334732:@Jonathan Ashwell]Unfortunately it’s an extremely complicated and inter-dependent set of classes. As you know, Charles Yeomans started the project and was the principle contributor. He posted on this forum some time ago that he’d cleaned it up and converted it to 64-bit, but after that he disappeared.
[/quote]
Sure - I have no idea what Charles is up to as of late
So it would seem despite it being widely used
Possibly BUT basically doing this means you banking on things that are planned for the future rather than addressing what is possible to deal with today
Suppose interops take longer than expected to achieve ?
Then what ?
I would try and do something today with what you have rather than hope something in the future fixes this for you
Unfortunately what has happened with macOSLib (where authors seem to have disappeared or abandoned it) can happen with ANY kind of code. Who knows - maybe Charles was hit by a bus or some other unfortunate fate befell him (not that I’m wishing this on him but maybe some accident happened) His code is still available and you or others could deal with it and update it
Should the same fate occur to Christian or Bjorn then what ?
I have no idea what plans they have in place should some unfortunate accident befall them.
Larger organizations are typically more capable of handling such an eventuality because they have that risk more spread out over more people.
I’d love to start the conversion today, but the only 64-bit option I’m aware of that can be used today to provide the functionality of MacOSLib is MBS. So let’s hope Christian looks both ways before he crosses the street.
We have backup plans. No worries.
Thats not what I meant
I literally meant “start working on moving MacOSLib to 64 bit”
Pretty sure Christian is immortal though…
Wasn’t he Samantha’s cousin on Bewitched? 
As noted above, if I could I would.