Creating Linked Lists in Objective C

Question

typedef struct {
    NSString *activty;
    NSString *place;
    float latitude;
    float longitude;
} event;

typedef struct {
    event *thing;
    Node *next;
}          


        

Answer 1

I think you'll find that it doesn't work in C++ (but they might have changed the grammar rules so that it does). You probably mean something more like this:

struct Node {
    event *thing;
    Node *next;
};

That works in C++ because Node is equivalent to struct Node if there isn't already something called Node (this sometimes causes puzzling errors when Foo is both a class and the instance method of another class, which happens in some coding styles).

The fix is to say struct Node. I prefer this; it seems more pure. There are some good reasons to use a typedef (e.g. things like TUInt64 which might have historically been a struct due to lack of compiler support). If you do use a typedef, there's no reason to give the struct a different name since they're in different namespaces (IIRC structs are a "tag namespace").

The usual typedef version is something like this:

typedef struct Node Node;
struct Node {
    event *thing;
    Node *next;
};

Alternatively, change the file extension to .mm and then it works because you're compiling Objective-C++!