Well, many unclear things in Xcode, particularly to package and SIGN an app build. So in continuation of the previous posts with tips and tricks for newbies, here are some more.

How to take a screenshot
The very intuitive shortcut is Command + Shift + 3. The screenshot is then silently saved as a PNG on your desktop.

How to enable Product > Archive
The Apple help says somewhere “Archive your product for submission to iTunes Connect or for sharing with others”. They say you first need to configure archiving in your scheme, but the described way to reach the Scheme editor is a bit outdated: now (Xcode 7.2) it’s Product > Scheme > Edit scheme. Anyway, in there go to “Archive” and give a name to your archive, as they say.
The problem is, even after doing that, Product > Archive was still disabled/greyed out. As it turned out, that was because the scheme destination was a simulator instead of “Generic iOS Device”. This is configured near the “play” and “stop” buttons at the top of the screen, where you usually switch between simulators. See below:

Once the target is properly set to this, Product > Archive should be enabled.

How to change the build and version numbers
The only tricky part here is to FIND where this is. They are located in the Info.plist file of your project. The version is called “Bundle versions string, short” and the build number is called “Bundle version”.

How to get Xcode to automatically fix your signing certificates
I’ll just relate my experience here, as fixing the signing certificates and provisioning profiles seems to have as many solutions as people with the problem. In my case, another developer had produced and built the initial version of the application, and then I took over the project, with the provisioning profiles but the the certificates that go with them.

After finally managing to unlock the damned “Product > Archive” menu item, I went ahead and clicked it. I ended up, at first, with a pretty confusing error message, saying: "Code Sign error: No matching provisioning profile found: Your build settings specify a provisioning profile with the UUID “8cda5448-xxxx-xxxx-xxxx-35c991b050b0”, however, no such provisioning profile was found". Searching for this, I got many “solutions” saying to copy ~/Library/MobileDevice/ (or ~/Library/MobileDevice/Provisioning \Profiles/) to various other locations, notably just /Library/MobileDevice/ (sudo required, of course). None of these worked for me, but one mentioned the fact that this error message could be caused by a missing certificate (say, if the provisioning profile is found but the corresponding certificate is missing, you still get that error message, how clear!).

By the way, you can find the location of your provisioning profiles by going to Xcode > Preferences > Accounts, then pick your team and View details, then you can “Download all” (that button apparently replaced the previous “refresh” button), and also right-click on any provisioning profile and choose “Show in Finder”. Yay! (see tip below to display the full path in Finder)

I was preparing myself to just create a hefty load of brand new provisioning profiles, but first I gave a shot to Product > Build For… > Running. And well, it got an error too, but unlike “Archive”, it explained that I should either import the previous developer’s certificate that matched the provisioning profile, or reset it, and it gave me the option to do the latter automatically. I accepted and hurray, it just worked. Then I was able to run Product > Archive, and to find said archive in Window > Organizer

In the Organizer, I tried to Validate the archive. I don’t remember it 100% (after all my struggles, I wasn’t really in the mood to take notes, sorry), but I believe it tried to sign the app too, and failed but also proposed to automatically regenerated the provisioning profiles. Note, by the way, that around this time I got an e-mail saying the prod certificate was revoked (because a new one was generated). In the previous step of building the archive, the dev certificate met the same fate. But it worked, and I ended up with a ready to upload archive, brand new certificates, and regenerated provisioning profiles. Yay 🙂 I just had one problem left, cf next “mini chapter” below.

How to solve a failed archive upload saying “Cannot verify client. (3000)”
Well in my case that was simple, I just restarted Xcode. Others have mentioned that doing a clean and rebuild (and re-archive) did the trick, I’d advise you to start with a simple restart, it’s just faster plus we just built the archive already, so I’m not convinced rebuilding it would change much, unless you do restart before rebuilding.

How to display the full path to current folder in Finder
By default, when something sends you to a folder in Finder (like, when you ask Xcode to open the folder containing your provisioning profiles), it seems impossible to find out where the said folder is as the left panel doesn’t contain a proper folder tree unlike Windows Explorer. Gladly something can be done about it, although it’s not that convenient: use View > Show Path Bar (or Alt + Cmd + P) to add a bar at the bottom of the window with the full path to the folder. You can then also use it to reach a folder among the folder’s parents (double click it).

I posted some tips and tricks in this previous post already, here are more as I discover them on my journey to getting used to Mac OS, Xcode and Objective-C (and some day Swift probably ^^)

How to type some of those characters that are totally necessary for programming
By this I mean things such as | (pipe / vertical bar), {} (braces / curly brackets) or [] (chevrons / angle brackets). That’s right, maybe you are luckier than I, but on the MacBook Pro I use for development, Apple thought it would be a good idea not to display those characters on the keyboard. Seriously WTF…
Anyway, here are the shortcuts, although note that I have a French “AZERTY” keyboard and it might sadly be different on yours :

• the pipe | can be obtained using Shift + Alt + L (thank god for this old blog post where I found it)
• the backslash \ can be obtained using Shift + Alt + / (slash) (thanks same blog post again)
• the braces {} can be obtained using Alt + ( (same key as 5) and Alt + ) (same key as °) (found it myself by pressing about every combination I could think of… reminded me how I used to push every button in Windows 3.1 as a kid, hurray for modernity!)
• the chevrons [] can be obtained using Shift + Alt + ( and Shift + Alt + ) (ditto)
• the tilde ~ can be obtained using Alt + N (for some crazy reason, all the “solutions” I found call the “Alt” key the “Option” key, go figure…)

How to reduce indentation of a bock of code
In Windows, reducing indentation of a code block is easy because the tab key (which is used to increase indentation) can be used to produce a reverse tab (by pressing Shift + Tab), and this reverse tab can usually be used to reduce indentation. In Mac OS I still haven’t found how to produce that reverse tab, but code indentation can be reduced the following way:
– select your block of code
– right click it
– in the contextual menu, look for Structure -> Shift Left

How to disable a specific deprecation warning with pragma
I prefer to keep all warnings on so as to be proactive about trouble, because in most cases a warning is likely to eventually turn into a nasty error. But this is not the case with every warning. Notably, you can’t get rid of deprecation warning if you want to keep supporting old iOS versions, for instance if you do something like

if(newFunctionExists) {
    doModernCode
} else {
    doDeprecatedCode
}

This is annoying because it puts an end to the quest to no warning in the project. Luckily, there’s a clean solution to this: you can disable the deprecation warning (or actually any other warning if you choose so) just around the block or line of code of interest. The code for this looks like:

#pragma clang diagnostic push 
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
[here goes your deprecated code]
#pragma clang diagnostic pop

(you may need to replace clang with GCC if you use the GCC compiler instead of clang) Pretty neat, isn’t it? 🙂
If you want to read more about pragma, I found this nice post, which is where I found out it could be used to disable warnings – after that all I had to do was find the codename of the deprecation ones.

Even neater, you can also define a macro, like this:

#define SILENCE_DEPRECATION(expr)                              \
{                                                                   \
_Pragma("clang diagnostic push")                                    \
_Pragma("clang diagnostic ignored \"-Wdeprecated-declarations\"")   \
expr;                                                               \
_Pragma("clang diagnostic pop")                                     \
}

#define SILENCE_IOS7_DEPRECATION(expr) SILENCE_DEPRECATION(expr)
#define SILENCE_IOS8_DEPRECATION(expr) SILENCE_DEPRECATION(expr)
#define SILENCE_IOS9_DEPRECATION(expr) SILENCE_DEPRECATION(expr)

And then use it like:

SILENCE_IOS7_DEPRECATION([here goes your deprecated code])

This way you can easily keep track of what code to remove when you eventually decide to drop support for very old iOS versions.

How to remove analyzer warnings from the list of warnings
As I was desperately trying to produce an archive (like this except that it doesn’t freaking work) of my app in an attempt to maybe manage to send it to other people so that they can test it (can’t believe the hell this is on iOS while it’s so trivial on Android), I “accidentally” analyzed my project. It gave me a few interesting warnings but also quite many not so relevant ones. So now my almost warning-free project is flooded with 50+ extra warning from the analyzer from Hell. Gladly, they can be purged, to do so, simply go to Product -> Clean : this will remove analyzer messages (as well as all warnings too) from the issue navigator. Then next time you build the normal warnings will come back, but not the ones from the analyzer (until you choose to run the analyzer again, that is).

How to disable word- / line-wrapping
Xcode Preferences (in the menu) -> Text Editing (in the top tabs) -> Indentation (that’s a clickable text in the top of the tab), in there you can check/uncheck Line wrapping
Source:
https://stackoverflow.com/questions/5271530/how-to-disable-word-wrap-in-xcode-4-editor

How to change iOS simulator language
You can simply use the Settings app in the simulator, just like on a normal device. Note that languages are shown in their own language, for instance “French” is “Français”, not “French”.

There is also an option that may be easier for switching back and forth between languages: you can run the app with a flag indicating the country, for instance add the flag -AppleLanguages (fr) for French.
This is explained more in details here:
http://abizern.org/2012/03/18/simple-localisation-testing/

Fixing some text getting automatically underlined in the app
This is cannot be changed by the app programmer as this is caused by a phone setting. So it’s up to the final user to disable it, in Settings -> General -> Accessibility, and then turning off Button Shapes.
Source:
https://apple.stackexchange.com/questions/124277/some-texts-automatically-underlined-in-iphone-5-with-ios-7-1

Solving error “attempt to present UIAlertController on [some UI] whose view is not in the windows hierarchy”
I got this one while replacing the more robust UIAlertView with UIAlertController. The main PITA from UIAlertController is that you need to feed it the current view as an argument, unlike UIAlertView which apparently just guessed it. This blog post pointed me to the solution for my case. Basically, UIAlertController must be called on the currently visible view, not on some other view (even if it does exist but is not on display right now).

Little bonus: here is the function I use to display a network error alert every time needed:

+(void) networkErrorAlert:(id)sender
{
     UIAlertController* alert = [UIAlertController alertControllerWithTitle: NSLocalizedString(@"Error",@"")
                                                                    message: NSLocalizedString(@"No Internet Connection",@"")
                                                             preferredStyle: UIAlertControllerStyleAlert];
     UIAlertAction* defaultAction = [UIAlertAction actionWithTitle: NSLocalizedString(@"OK",@"")
                                                             style: UIAlertActionStyleDefault
                                                           handler: ^(UIAlertAction * action) {}];
     [alert addAction:defaultAction];
     [sender presentViewController:alert animated:YES completion:nil];
}