How to assign a variable inside a block in Objective-C

I recently tried to assign a value to a variable I had declared from inside a block. Apple’s frameworks make frequent use of blocks, and as such, I didn’t see anything wrong with this code:

Xcode 9 begged to differ though, telling me that the “Variable is not assignable (missing __block type specifier)“.

Stumped, I had a look around the web, where I found this StackOverflow article that explained it. My mistake was that when I declared the variable above the block. I had no idea this was necessary, but apparently it is.

All we need to do is add “__block” in front of the variable at the time we declare it (more or less precisely what Xcode was trying to say). The error message disappears when we amend the code like this:

Easy – if you know how 🙂

One thought on “How to assign a variable inside a block in Objective-C

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.