Automatically creating class instances

Question

Is it possible to create dynamically instances of a class giving them specific names (e.g. Friend1, Friend2, etc)?

I have a "Friends" class with some instance variables (e.g. Name and Surname). In my app user selects from a list the number of "Friends" he wants to add. So in case he selects 5 the UITableView will be populated with 10 empty fields (Name and Surname).

Do you know any way to create these objects "on the fly"?

Could you give an example of what exactly you are after? if the user selects N items, create a mutable array and fill it with N new items and let the user fill the data ... — Dan Shelly, May 06 '13 at 18:34

score 0 · Answer 1 · answered May 06 '13 at 18:33

0

When he selects 5, create an array of friends:

friends = [[NSMutableArray alloc] init];
for (int i = 0; i < 5; i++)
    [friends addObject:[[[Friend alloc] init] autorelease]];
[tableView reload];

(where friends NSMutableArray is declared in interface section of your view controller)

And in UITableViewDataSource:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (section == friendsSection)
        return [friends count] * 2;
    else ...;
}

I leave -tableView:cellForRowAtIndexPath: implementation as an exercise to the reader, it depends on too many details you didn't describe.

answered May 06 '13 at 18:33

My example does not utilize proper resource management and probably other details are missing, of course. – May 06 '13 at 18:36
I thought that I needed to know the names of the objects in order to store user input. – V. Pier May 06 '13 at 18:37
You may treat `friends[n]` as a name of object, if you want think that way. – May 06 '13 at 18:39

score 0 · Answer 2 · answered May 06 '13 at 19:08

Well, your problem is solved, good! But your question addressed also a problem that is not yet solved: "to create dynamically instances of a class giving them specific names", so that you can refer to them later using these names.
Referring to an object essentially means to send it a message. In the Objective-C runtime, this is done using objc_msgSend(id theReceiver, SEL theSelector, ...). Thus you need a pointer to theReceiver. I interpret you question so as "is it possible to associate the pointer to a new instance with a dynamically created name. I think this is possible using a dictionary like so:
You create dynamically your identifier: NSString *myIdentifier = @"anyString"; or any other way to create a string. Then you create an instance of your class: MyClass *myObject = [[MyClass alloc] init]; or any other way to instantiate it. Eventually you establish the association: NSDictionary *dict = @{myIdentifier: myObject};
Later you can send the object a message, using the object's name as [[dict objectForKey:myIdentifier] message];
Maybe there is an easier way to do it...

Automatically creating class instances

2 Answers2