Basic Objective C class to return an array

Question

I am new to Objective C and am trying out some basic concepts but hitting a few brick walls

Essentially what I am trying to do is write a class that returns an array when messaged from another class

The class that returns the value would be something like -

ReturnClass.h

#import <Foundation/Foundation.h>

@interface ReturnClass : NSObject {

}


-(NSMutableArray *) getLocation ;


@end

ReturnClass.m

    #import "ReturnClass.h"

    @implementation ReturnClass

    -(NSMutableArray *) getLocation {
   //do some stuff to populate array
    //return it
        return  latLngArray;
    }
    @end

I then wanted to call this in to another implementation in order to harvest the value

SomeOtherClass.m

#import "ViewController.h"
#import "ReturnClass.h"

@interface ViewController ()

@end
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
NSMutableArray *latLngArray = [[getLocation alloc] init];
}

I appreciate there is probably a fair bit wrong with this but please be gentle as I am trying to learn :)

Classes don't return things, methods do. And you don't alloc methods. — Hot Licks, Apr 17 '13 at 14:57
(You need to go back and find a good description of what "objects" are and study it.) — Hot Licks, Apr 17 '13 at 14:58
Trust me -- A few hour spent understanding the basic concepts of objects will do you a lot of good. — Hot Licks, Apr 17 '13 at 16:50

score 4 · Accepted Answer · edited May 23 '17 at 10:24

The call would looke like this:

- (void)viewDidLoad
{
    [super viewDidLoad];
    ReturnClass *retClass = [[ReturnClass alloc] init];
    NSMutableArray *latLngArray = [retClass getLocation];
}

This would give you the array produced by getLocation.

This code makes a new instance of ReturnClass every time it needs the array; this may or may not be what you want, because you cannot keep any state between invocations. If keeping state in ReturnClass is what you need, you would have to implement a singleton (here is a link to a question explaining a very good way of implementing singletons in Objective C).

Ah that makes more sense, I need to instantiate before I can call the method - thanks! — user499846, Apr 17 '13 at 15:07

score 1 · Answer 2 · edited Nov 03 '13 at 16:01

1

You should review your concepts of object oriented programming in general. In particular, do not confuse a class with a method.

In your code, you have to instantiate a ReturnClass instance first to be able to call its method getLocation.

edited Nov 03 '13 at 16:01

Josh Crozier

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answered Apr 17 '13 at 14:50

ilmiacs

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score 0 · Answer 3 · answered Apr 17 '13 at 14:51

NSMutableArray *latLngArray = [[getLocation alloc] init];

For starters, this line misses the mark. You're sending +alloc to the name of a method. You should be sending that message to a class, like this:

ReturnClass *myObject = [[ReturnClass alloc] init];

and then sending messages to the resulting object, like this:

NSMutableArray *latLngArray = [myObject getLocation];

Basic Objective C class to return an array

3 Answers3