Question

this is from apple block programming, can anyone tell me what it means

Stack (non-static) variables local to the enclosing lexical scope are
captured as const variables.

Answer 1

Say you have:

int i = 5; // in stack

Then in block you have:

...
i++; // can't do that, because i now inside the block is a const
...

You’re going to add __block to i declaration to be able to change value of i inside a block like this:

__block int i = 5; // remove __block and see the error

void (^myBlock)(void) = ^{
    NSLog(@"[inside block] i = %i", i); // no error even without __block
    i++; // error here without __block
};

myBlock();

NSLog(@"[outside block] i = %i", i);