Changing UI from a background thread

Question

I getting an error that Iam changing the autolayout engine from a background thread , is there's a way to know which block of code makes this warning ? or I just have to search for it by myself ?? Thank you.

Answer 1

Probably there is a better answer but I would start by putting

for Swift:

assert(NSThread.isMainThread(), "Expected code to be called on main thread");

for Objective-C:

NSAssert([NSThread isMainThread], @"Expected code to be called on main thread"); 

to all sections of your code you're suspicious about.

This way app will crash if you're doing that code not on main thread.

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Is this error an error or is it an exception? If it is exception you can try to catch it using exception breakpoint like here: How to debug “Collection was mutated while being enumerated” errors and like, when Xcode does not provide me with enough information? ?

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After having looked at your exact message looks like what you need is:

This code PSPDFUIKitMainThreadGuard causes assertions on UIKit access outside the main thread

taken from iOS9 - This application is modifying the autolayout engine from a background thread — where? .