The following code is returning an expression unused warning on the assignment operation in the block. The code isn't very practical, but there is a lot more code in the excluded section and that code has to run on a particular queue. 

__block NSNumber *pageId=nil;
dispatch_sync(_myDispatchQueue, ^{
    int val;
    //... code generates an int and puts it in val
    pageId = [NSNumber numberWithInt:val];
}];
//pageId used below

How do I get rid of this error?

warnings clang objective-c-blocks
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