In terms of language features, mulle_objc resets the basis of Objective-C back to ObjC 1.0 and cherrypicks improvements from the later versions.
Differences to Objective-C 2.0
Do not use the “not planned” features even if the mulle-objc compiler might still understand them. The runtime or the linker will not support them.
| Topic | State | Link |
|---|---|---|
| @encode() | supported: 90% the same as the Apple runtime | (what is this ?) |
| @package | never: will produce an error | |
| @synchronized() | not planned | (what is this ?) |
| ^blocks | not planned: [^3] | (what is this ?) |
| atomic | not planned: atomic as default: never | |
| BOOL | supported: but it is an int. If you really need to use bool use _Bool. |
|
| @import | not planned | (what is this ?) |
| nullable | not planned: will produce an error [^2] | |
| readonly | supported: but an ivar will be synthesized | |
| weak, strong | never | |
__bridge |
will be a nop #define (also __bridge_retained, __bridge_transfer) |
|
__unsafe_unretained |
could be a nop #define (_autoreleasing) |
|
| ARC | never: but look for mulle-objc’s AAM | (what is this ?) |
| @implementation() | never: class extension with added instance variables don’t work | |
| NSArray<NSString* > | never: generics are not in the cards | (what is this ? |
| ObjectiveC++ | never: But the mulle-objc instance memory layout should be this->__vtab compatible to allow dual facing objects. |
|
| NSArray *foo; foo[ 1] | not planned: [^1] what is known as “Subscripting” | (what is this ?) |
| Non-fragile ivars | never | (what is this ?) |
| property dot syntax | not planned: [^1] | (what is this ?) |
| Protocol | never: Protocol as a class is gone. You have to use PROTOCOL instead of Protocol * |
|
| variadic arguments (:…) | supported: but not compatible to <stdarg.h> |
Appendix
Footnotes
[^1] : This is basically operator overloading, which is un-C like.
[^2] : Superflous keyword, ObjC is by design nullable. It only makes sense to adorn non-nullable parameters.
[^3] : GCD is a Apple technology, that really needs kernel support to work well. lambdas are not a part of C11. Generally I find blocks unconvincing. It might be an idea to make NSInvocations out of block syntax ?
Glossary
| Wording | Meaning |
|---|---|
| not supported | might just accidentally work |
| not planned | never say never, but this probably won’t happen |
| never | sometimes you have to say never :) |
Terminology
For the discussed concepts and terminology check any of the following links.
- Wikipedia: Objective-C
- Apple: Objective-C Feature Availability Index
- NSHipster: @compiler directives
Next
With all the theory under your belt, you’re ready to start your own development.