Too much C-Style in Objective-C programs?

Question

Hi I'm writing this question because I'm a newbie in ObjC and a lot of doubts came to my mind when trying to make my fist training app. The thing is that I have a strong background in C, I've been programming in Java for the last year and I've done some collage stuff with Smalltalk (I mencione this because those are my programming references and those are the languages I'm comparing ObjC with).

The first problem I've encountered is that I don't know where to draw a line between ObjC and C, for example when dealing with math operations, Should I use math.h or there is a more "object-way" like you can do in Smalltalk (aNumber raisedTo: 3) ? How does a person with no background at all in C learns ObjC?.

Another thing that I couldn't find was a collection's protocol (I've looked over the Foundation Framework documentation given by Apple). Because I want to implement an expresion tree class and I wanna know if there are methods that all collections should implement (like in Smalltalk or Java) or I gotta check by hand every collection and see if there is a cool method that my new collection should have.

I don't know if I'm being too stupid or I'm searching for features that the language/framework doesn't have. I want to program in ObjC with the ObjC style not thinking in C, Java or Smalltalk.

Sorry if the question was too long.

Answer 1

Absolutely use <math.h>. You don't way to pay message sending overhead for functions that run in 30 cycles. Even function call overhead seems pretty steep at that point.

More generally, use as much or as little of C-style as you want to. I've seen Objective-C that was nothing but a couple C modules glued together with objective C messages, and I've seen Objective-C that essentially zero lines of code without the square brackets. I've seen beautiful, effective code written both ways. Good code is good code, however you write it.

Answer 2

Try to use each language for what it's good at. IMHO, this would include Obj-C objects but C-like code implementing methods. So use math.h and concise C code to implement logic, but don't be shy about using Obj-C classes to organize your larger blocks of functionality into something that makes sense.

Also, try to interact with the frameworks using their style so you're not running upstream.

Answer 3

In general, you'll use C features for numerical calculations. You'll generally use objects for most other things. The reason for this is that objects are way heavier than a simple scalar — there's just no benefit to it. Why would you ever write [[NSNumber numberWithInteger:1] numberByAddingNumber:[NSNumber numberWithInteger:2]] when you can just write 1+2? It's not only painful to read, it's far slower and it doesn't gain you anything.

On the other hand, Cocoa has rich object libraries for strings, arrays, networking and many other areas, and using those is a big win.

Knowing what's there — and thus what the easiest way to do something is — is just a matter of learning. If you think something should be there and you can't find it, you can ask either here or on Apple's Cocoa-Dev mailing list.

As for a collection protocol — there really isn't one. The closest thing to it is the NSFastEnumeration protocol, which defines precisely one method: countByEnumeratingWithState:objects:count:. This lets you use the for (id someObject in someCollection) syntax to enumerate the objects in a collection. Otherwise, all the collections define their own independent interfaces.

Answer 4

The first problem I've encountered is that I don't know where to draw a line between ObjC and C.

My rule is to use C wherever it makes sense to you. Objective-C has the benefit of letting you choose when to be procedural and when to be object-oriented. Go with what fits best with the code you're writing.

Another thing that I couldn't find was a collection's protocol [...] I want to implement an expresion tree class and I wanna know if there are methods that all collections should implement (like in Java) or I gotta check by hand every collection and see if there is a method that my collection should have.

Unlike Java, Objective-C does not have a master protocol for collections like the java.util.Collection interface. Also, there aren't a proliferation of specific container implementations as in Java. However, that gives you the freedom to implement a collection in a way that makes sense for your code.

For building a tree-like structure, you might take a look at NSTreeNode to see if it might be useful to leverage. (It may be more than you're need or want, but might be worth a shot.)

As far as rolling your own collection, I've learned a lot while creating CHDataStructures.framework, and you're welcome to use whatever you like from that code, or just look at my attempts at creating Cocoa-like structures, designed to complement the Foundation collections and operate similarly. Good luck!

Answer 5

As has been mentioned, there’s no real protocol for abstract collection classes (aside from the NSFastEnumeration protocol which provides the for(id item in collection) syntax when implemented), but there are conventions to follow.

Apple’s Introduction to Coding Guidelines for Cocoa covers some of this, and there is in fact a section on naming collection methods which covers the general cases (though note that generic container classes such as NSArray use the term “Object” as opposed to “Element” listed in the examples there – i.e. addObject:, removeObject:, and so on).

Following the patterns listed here (among others) is actually crucial when you want your classes to be KVC-compliant, which allows other users to observe changes in your object’s properties.