Question

I am looking at Objective-C and I notice, for example, a class-interface declaration begins with @interface. Fine, no problema. The text, therefore, suggests no space is permitted between the @ and interface. However, when I pass the following simple example to the GCC compiler in a *.m file:

@ interface A
@ end

the compiler accepts the code without complaint. Can Anyone point Me in the direction of a reference which says explicitly whether or not @ interface is also considered acceptable by the Objective-C specification? I found nothing in Apple’s 2008 and 2011 documents to say one way or the other besides the simple text alluded to earlier in the question.

Thanks in advance.

EDIT: It may be worth noting Emacs performs text coloring based on whether the identifier is a keyword or not; keywords are blue and non-keywords are yellow. The @interface colors blue and @ interface colors yellow. Similar behavior occurs in Vim.

Answer 1

There is no formal specification for Objective-C (beyond The Objective-C Programming Language). There’s definitely no BNF-style definition of the whitespace conventions. If it compiles, that’s about the closest we have to “legal.” This is true of many languages. Perl for instance is best defined as “those strings which the perl executable will not reject.” (At least in my opinion….)

That said, the correct style is @interface without a space. See Defining a Class.