Objective-C Blocks Syntax

Presentation version of my blog post about how the blocks syntax came to be in Objective-C that I made for CocoaKucha NYC on November 20th 2013.

You can find the original blog post at http://nilsou.com/blog/2013/08/21/objective-c-blocks-syntax/

Transcript

1. I’m Nils Hayat @nilsou online.
2. Objective-C Block Syntax
3. Objective-C Blocks • Introduced in OS X 10.6 / iOS 4.0 • Autonomous piece of code • Capture their environment
4. Declarators • 2 roles • Give the type of variable • Name the variable ! • Ex:
5. Reading rules • Start from the identifier • Go right until you can’t • Then read to the left of the variable
6. Modifiers • Pointer Modifier: * • Array Modifier: [] • Function Modifier: () • Block Modifier: ^
7. Pointers • a is a pointer to an int. • Immediately to the left of the modified variable
8. Array • a is an array of ints. • Always to the right of the array. • Can be completed by the dimension: int a[10];
9. Function • f is a function that returns an int • can be completed by the type of the arguments • Always to the right of the variable
10. Precedence • Similar to * / + - • [] and () have higher precedence than * and ^ • This explains rule right then left • You can compose multiple modifiers
11. Pointers and Arrays ! • a is an array of pointers to ints. ! • What if you want a pointer to an array of ints?
12. Arrays and Functions • You cannot compose [] and () • No array of functions • No function that returns arrays ! • f is a function that takes an array as an argument
13. Pointers and Functions ! • f is an function that returns a pointer to an int ! • What if you want a pointer to a function?
14. The block pointer modifier • Similar to function pointers • ^ (caret) can only be applied to a function • the ^ symbol and the identifier ALWAYS NEED TO BE BETWEEN PARENTHESIS
15. Abstract Declarators • Declarator has 2 roles (give the type of variable & name it) • abstract declarator has only one role : give the type • just remove the identifier from a declarator!
16. Abstract Declarators • Used in 3 places in standard C • In casts: int *a; long *b = (long *) a; • in sizeof(): malloc(sizeof(long *)); • When declaring arguments type for a function: int f(long *);
17. Abstract Declarator • Objective-C uses them in one more place • For methods’ return values or argument types - (long **)methodWithArgument:(int *)a;
18. Block Abstract Declarator • Write the concrete declarator • Remove the identifier
19. Example
20. Thank You http://nilsou.com