You may have expected to see
99 printed in the console because in the pulsing example, you were able to successfully modify
self.taxiWidth.constant. This has to do with how the block’s execution stack is created. Figure 13-1 shows that the stack has a read-only (italicized) copy of each variable. The values are frozen at the time the block is created.
Although the block’s copy of
self is not modifiable, the value is still the address for the same
aboutViewController object. The properties can still be changed, as can any part of those properties.
aNumber is not a ...