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

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!