IOS __block Variable Scope

See

In the C language, 2 Independent functions are not able to access local variables (inline?). But block provides this function, it can not only read variables, but also write to the variables! Indicates that the block obtained the last true value of I 5, not just 0, which is the function of __block. See J again, because there is no __block prefix, only achieved 0, did not get 5. The function of __block is simply to copy a copy into the heap and maintain the copy's survival, so you can use the local variables in the function that has ended.