mulle-objc: present and absent language features
Continued from mulle_objc: inheriting methods from protocols of the mulle_objc series.
Updated: 7. November 2016
Objective-C is now a hybrid of many languages. The timeline being approximately this:
ObjC 1.0: C plus Smalltalk
<- appeasement of the Java Noobs
ObjC++
ObjC 2.0
<- usurpation by the C++ Flagellants
mulle_objc is supposed to put the basis of Objective-C back to ObjC 1.0 and cherrypick improvements from the later versions.
Here is a list of what’s going on and what will be going on and what will not happen. Taking most of the terminology from:
The separation between Compiler, Runtime and Language is of course a bit arbitrary.
Language
| Topic | State |
|---|---|
| BOOL | supported: but it is an int. If you really need to use bool use _Bool. |
| @”string” | supported |
| @1, @(), … | planned: what is known as “Literals” |
| NSArray *foo; foo[ 1] | not planned: [^1] what is known as “Subscripting” |
| @defs() | supported |
| @encode() | supported: 90% the same as the Apple runtime |
| @package | never: will produce an error |
| @property | supported |
| @autoreleasepool | supported |
| @synchronized() | not planned |
| @compatibility_alias | unknown |
| @try @catch | supported |
| for ( i in x) | supported: what is known as “Fast Enumeration” |
| nonatomic | supported |
| atomic nonatomic | not planned |
| atomic as default | never |
| instancetype | supported |
| generics | never |
| nullable | not planned: will produce an error [^2] |
| nonnullable | supported |
| property dot syntax | not planned: [^1] |
| Protocol | never: you have to use PROTOCOL instead of Protocol * |
| weak, strong | never |
__bridge |
will be a nop #define (also __bridge_retained, __bridge_transfer) |
__unsafe_unretained |
could be a nop #define (_autoreleasing) |
Compiler
| Topic | State |
|---|---|
| Default synthesis | supported |
| ARC | never, but look below for AAM |
| Exceptions | supported |
| static NSStrings | supported |
| variadic arguments (:…) | supported, but not compatible to <stdarg.h> |
Runtime
| Topic | State |
|---|---|
| Non-fragile ivars | never |
| ^blocks | not planned: [^3] |
| Fast enumeration | supported |
| ObjectiveC++ | never: But the mulle-objc instance memory layout should be this->__vtab compatible to have dual facing objects. |
| Class extensions | never: at least when you want to add instance variables |
| Modules | not planned |
Other “planned” features
For some of the “supported” features like protocol inheritance, please read the complete series.
| Topic | State |
|---|---|
| AAM | supported: a much simpler successor to ARC called “Always Autoreleased Mode” |
| Generated parameter compliancy asserts | planned: with a special compiler option each object parameter of a method will be checked with NSParameterAssert for class compliancy. Here nonnullable will be useful. |
| Method chaining | technically supported: you can search the runtime to supply you with the overridden methods. But it’s slow. |
[^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 |
|---|---|
| supported | should work already |
| will be supported | must work with the first release |
| not supported | might just accidentally work |
| planned | may not be in the first release |
| unknown | neither “planned” not “not planned” |
| not planned | never say never, but this probably won’t happen |
| never | sometimes you have to say never :) |
Continue to mulle-objc: the trouble with property
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