What does "->" mean in objective-c?

Question

Well, I'm sorry I can't find any useful results when I search "->" on Google, and this is the first time I've seen anything like this. I've found the following line in one of Ray Wenderlich's game center tutorials:

Message *message = (Message *)[data bytes];
if (message->messageType == kMessageTypeRandomNumber) {
    ...
}

Message here is a predefined struct:

typedef struct {
    MessageType messageType;
} Message;

From http://www.raywenderlich.com/3325/game-center-tutorial-for-ios-how-to-make-a-simple-multiplayer-game-part-22.

Is there somewhere I can read more about this sort of syntax? Thanks! — Flying_Banana, Mar 22 '14 at 03:00
probably here http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B . — Coldsteel48, Mar 22 '14 at 03:03
Pretty much exactly the same thing it means in C or C++, which you should know before you attempt to program in Objective-C. — Hot Licks, Mar 22 '14 at 03:08
Well, I self-taught. There are things I don't know. Why are you guys just down voting because I want to know something I can't get from google? — Flying_Banana, Mar 22 '14 at 03:09
You should know how to program simple C before you attempt to deal with Objective-C. You apparently don't even know what a pointer is, which bodes ill for your future efforts. — Hot Licks, Mar 22 '14 at 19:29

score 3 · Accepted Answer · edited May 23 '17 at 12:05

3

This means the same thing as it does in C and C++, basically you are accessing the data of a pointer.

If you were using an object: you might say message.messageType

Since you are dealing with a pointer: you use message->messageType to get the messageType data from the pointer message

This syntax saves you from having to dereference a variable before you access its data.

Here is a link to another StackOverFlow question which was asked from a programmer learning C. The same content/principles apply here. Arrow Operator

Here is another link explaining the Difference Between . and ->

edited May 23 '17 at 12:05

Community

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answered Mar 22 '14 at 02:59

Josh Engelsma

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... so the number one use for `->` nowadays is probably accessing unexposed member variables on a variant of `self` that has been deliberately kept weak and then made strong again for the benefit of an asynchronous block. – Tommy Mar 22 '14 at 03:18

What does "->" mean in objective-c?

1 Answers1